Twitter is obviously the most used microblogging today. Information updates are happening really fast in here, often faster than traditional news portal. This is why search engine giants think why don’t also give people tweets in the search result… in REAL TIME.
Bing sees numbers of followers in the ranking system. That means a user with more followers has the bigger chance to be the king of the hill. Be careful on tweet duplicating, the penalty will be the same as duplicate content of conventional web page; your tweet would rank lower.
Google uses different criteria. Instead of number of follower Google is more interested in followers reputation. The system works similarly with Google Page Rank system. The more a user is mentioned by the followers, the more reputation he has.
Another rumour is Google will also use geo-location data to determine the rank of tweets. No detail about this has been come out. Let’s just wait how huge this Google and Twitter collide.