Sean Suchter, general manger of Microsoft's Silicon Valley Search Technology Center, wrote in a blog post that the Twitter results are limited to searches on "some of the more prominent and prolific Twitterers from a variety of spheres." These would include tweets from folks like Danny Sullivan or Kara Swisher, as well as those from Al Gore or Ryan Seacrest, people with more general consumer appeal.

Search results will include Twitter, the person's name, latest tweets in real time, along with an easy link to "See more tweets" from the person. The feature rolled out gradually on Wednesday. Suchter says Microsoft picked a "few thousand people to start based primarily on their follower count and volume of tweets."

It turns out that people searching for tweets on Twitter need to add "Tweet" in the search term to get the latest in the results query. For example, searching on "Danny Sullivan" returns images of Danny Sullivan, Search Engine Land, and the Wikipedia page as the No. 1, No. 2 and No. 3 results, respectively. Search on "tweet danny sullivan" and the first item in the query returns a tweet.

Microsoft is hardly the first to serve up Tweets in search results. A host of others have tapped into Twitter through application programming interfaces (APIs) to pull in Twitter streams, too. Some lesser-known search engines include Search3.com and Spezify.com.

Whitney Burk, Bing's director of communications at Microsoft, says there are technical limitations from Twitter as to how much information sites can index through the public API. "We're not trying to get around the technology issues, but we are very interested in the possibilities around real-time search," she says.

It's too early to tell how pulling tweets from Twitter would influence search engine optimization, paid search or display advertising, Burk says. Nor is it clear which steps Bing will take to filter the increasing amount of pornographic material that is surfacing on Twitter pages and in tweets, if Microsoft has an opportunity to pull and index all tweets from the site.

"Obviously, we're not interested in doing anything offensive to anyone," she says. "The sources we index now are public personalities -- the most prolific Twitters in the public sphere, so I think today the risks are low."

Real-time search will provide challenges for search engines. Not just Bing, but others, too. As far as the potential of explicit content appearing in tweets, Microsoft says it aggressively tries to filter adult content feeding from Twitter into Bing. In fact, this is the major cause of any slight delay when not seeing the freshest and latest tweets.

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