When Twitter users go to post a new tweet, they have in the past used a button that says "update" (at least from Twitter.com...that varies when you get into all the different apps Twitter users use). Now, that button says "Tweet".

We're not sure exactly when the change was made, but it appears to have been very recently, as there is quite an outpour of Tweets from users mentioning that they are now seeing the "tweet" button. Perhaps this is Twitter way of asserting some kind of ownership of the word and the brand that it carries.

Twitter made "retweeting" an official feature last year, after the community-born practice grew to mainstream use.

Interestingly, Retweet.com just sold for $250,000 this week.

The tweet button isn't the only new thing going on with Twitter's website this week. Twitter is currently in the process of rolling out geolocation features on the site, after having had such capabilities available via the API since November.

Twitter CEO Evan Williams will be speaking at SXSW early next week (WebProNews will be there covering it). We may get more interesting news from the company there (some expect an ad platform to be announced).

Update: Looks like some have noticed this for at least a couple days.

Last week, we reported that Facebook wanted to hire two people in Washington, D.C., and then dissected the official descriptions of the positions as best we could.  Still, the bullet points left a lot unclear, so it's noteworthy that Facebook provided some clarifying paragraphs today.

Adam Conner was the first member of Facebook's D.C. team, and a post he wrote for the company's internal blog was actually promoted to its public blog this afternoon.  Conner - who also deserves applause for being a Conan supporter - did a good job of explaining some of his responsibilities and favorite moments.

Here's one excerpt that reveals just how politically connected Facebook may be: Conner wrote, "The week of January 11-17 was pretty cool, helping to pull together the Global Disaster Relief Page in just few hours.  I went on vacation that weekend and was on the phone in Mexico convincing President Clinton to plug our Facebook page as part of the relief efforts."

As for the more day-to-day stuff, Conner described his duties by writing, "I get to sit in meetings with vaguely important and occasionally actually important people and explain why Facebook is like the wheel or fire and how not using it really isn't an option anymore."

It sounds like the social network's well on its way to being omnipresent in Washington, then, especially as it adds two more employees.

Users of the mobile version of Google Product Search can now see if items are in stock at a local store from select retailers. These retailers include: Best Buy, Sears, Williams-Sonoma, Pottery Barn, and West Elm.

Product listings from these retailers will have blue dots that can be tapped to see an "in stock nearby" link, which takes you to a seller's page where it will either say "in stock" or "limited availability". In addition, these pages will show you how far away the store is from your location (assuming you have My Location enabled or have manually specified your location).

The feature is available for iPhone, Palm WebOS, and Android users in the U.S. Users can hit the "more" link, and select "Shopping" or find the "Shopping results" section in Google's Universal Search results when searching from Google.com.

Google offers a form for retailers who are interested in participating in this program. Google says to make sure you have your Local Business Center data up to date and to ensure your Product Search data is in "great shape."

A Google exec recently said, "In three years' time, desktops will be irrelevant." That's debatable, but there's no question that mobile use will have grown much more than it already has. Based on comments in a recent keynote, Microsoft CEO Steve Ballmer doesn't seem to think PC use is going to drop too much, but he did say, "Mobile queries are just going to keep going up and up and up."

Do you think desktops will be irrelevant in 3 years? Share your thoughts here.

A study released last month found that the number of mobile phone subscribers is on track to increase from 4.6 billion to 5 billion globally by the end of 2010. Another study found that consumers are getting more comfortable with mobile shopping.

Mobile Search

Google has dominated the search market for a long time, and while this still continues to be the case, it's important to note that search in general changes with mobile. People are searching in different ways than just using their favorite search engines. They're using different apps. They're using their voices. They're scanning barcodes for instant access to product information. The number of ways people are finding information with their phones is only going to keep increasing. On mobile, it's not just about Google, Yahoo, and Bing.

That's not to say these three aren't still incredibly important to mobile. In fact, the search share among these top search engines may even become more greatly divided as time goes on. We're seeing different mobile carriers and manufacturers making deals with these companies, which affect the default search options for various devices. As we discussed before, mobile search engine use may be largely dictated by device popularity, which is (in my opinion) one of the biggest things Bing will have going in its favor in terms of market share - Microsoft's new Windows Phone 7 phones will come with Bing hardware keys, meaning the most convenient way to search on these devices will likely be to hit a single button taking the user to Bing. If these devices become popular, it could be huge for Microsoft in search.

As far as Google indexing and mobile sites goes, Google's Matt Cutts says, "If you can find a way where your existing site will work well in mobile browsers, we're not worrying about supporting two completely different sites."

To learn about this subject in more detail, read the Google Webmaster Central Blog posts: Help Google Index Your Mobile Site, and Running Desktop and Mobile Versions of Your Site.

Mobile Search Advertising

When it comes to AdWords, Google says to create separate, mobile-focused campaigns so you can optimize keywords, ad text, and landing pages for people using mobile devices. Google shared an interesting case study this week looking at Razorfish's mobile AdWords approach. They shared the following details:

- The Razorfish team started by duplicating the existing desktop campaigns and switching the settings to target mobile devices with full internet browsers.

- Since their client had a well-known brand name, they focused on branded keyword terms with enough traffic to help them learn quickly about what was working best for their campaigns.

- To measure performance, they tracked several conversion metrics including whether a mobile user looked up the brick and mortar store location or downloaded a coupon from the website. Right away, they saw a 7.5% lower cost per conversion on mobile devices, encouraging them to test ways to optimize their mobile campaigns.

- Razorfish tested whether variations in the campaign's landing page would affect conversion rates. The team hypothesized that mobile users might be looking to take a specific action, and by starting the user's experience closer to that action, the client would see better results. As it turned out, for this client, they saw much higher conversion rates when the user was directed to a landing page that showed nearby store locations.

- Finally, they tested variations in the ad text. Four versions of ad text were tested, including the original copy used in desktop campaigns. Each of the three new versions provided over 9.3% lift in conversion rate over the strongest performing copy in their desktop campaigns.

When it comes to Yahoo and Microsoft search advertising, things are about to get more appealing here in general, and presumably, that includes mobile. Microsoft and Yahoo advertisers will have the audiences of both search engines to view ads once Yahoo and Bing get their integration done.

Wrapping Up

One of the most important things any search marketer can do with regards to a mobile strategy, is to simply keep up with the latest mobile trends and innovations. This space is rapidly evolving, and new apps are released frequently. Pay attention to hot apps, and how your target audience is engaging with them. What devices, operating systems, and browsers are hot? Monitor studies and surveys that delve into demographics. Try to stay ahead of the curve.

Do you have a mobile search strategy? What suggestions do you have for improving in this area? Comment.