UPDATE (8:43 a.m. PDT): Microsoft has struck a deal with Facebook to include its news feed updates in Bing’s searches.  Bing powers search on Facebook.

Tweets from users on Twitter have hit the big-time: they’re now going to be featured in search results on Bing and Google.

For those geeks among you who follow news from places like Twitter, Google and Microsoft (maker of Bing) like I do (it’s not a particularly scintillating life I lead…), you were no doubt enthralled with yesterday’s unfolding events.

First there was this blog post by Biz Stone, Twitter’s chief:

…there are already tens of thousands of Twitter apps and more to come because people want the choice to consume and create tweets wherever and whenever they prefer. The folks over at Bing took a keen interest in Twitter and worked fast to establish a working relationship with us in line with our open approach.

Twitter is providing Bing access to the overwhelming deluge of public, real-time tweets rushing in from all around the world so they can help you find those that make the most sense right now. While Twitter currently presents tweets based simply on timeliness, Bing is experimenting with new solutions such as “best match.” We hope more working relationships with organizations in the search business will mean even more variety for users.

Which, of course, was a not-so-coy reference to Google (OMG!) Sure enough, the ever-present and elegant Marissa Mayer, Google’s chief guru around all things search, sent a tweet (”Google and Twitter!! Yay!! http://bit.ly/183svN“) announcing they, too would integrate tweets from Twitter. From her blog post:

…we are very excited to announce that we have reached an agreement with Twitter to include their updates in our search results. We believe that our search results and user experience will greatly benefit from the inclusion of this up-to-the-minute data, and we look forward to having a product that showcases how tweets can make search better in the coming months. That way, the next time you search for something that can be aided by a real-time observation, say, snow conditions at your favorite ski resort, you’ll find tweets from other users who are there and sharing the latest and greatest information.

Here’s Yusuf Mehdi, a senior vice president at Microsoft, previewing Twitter integration with Bing search results at this week’s Web 2.0 Summit here in San Francisco:

This is great for users because Twitter is often the place to get first-person, “on-the-ground” reports of breaking news or leaking information. By seeing real-time results of tweets from Twitter relating to any given topics in context with other information, particularly reports researched, verified and edited by professional journalists, can be a powerful way to stay informed. It’s also a great way to forensically understand how it is events unfold because there are so many points of view on the event.

It’s great, too for advertisers on Google and Bing who bid on search keywords. Because there is a finite amount of search inventory for the vast majority of keywords, any opportunity to increase the volume of searches overall creates more opportunities for advertisers to insert relevant messages when and where audiences are expressing a related interest. The challenge for advertisers, of course, is keeping track of rising and falling memes (or topics) in order to place timely bids on keywords or phrases relating to those topics or issues that are suddenly on the rise. Still, it’s an opportunity.