As a result of a new deal between Google and Twitter, we'll soon be seeing tweets pop up in Google searches just like all other results, if the content is relevant. For Twitter, this is a big move to help bring more people to the site, and generate more pageviews for advertisers, while for Google, it improves its spidering in order to provide more relevant results.
Prior to this deal, Google had to spider Twitter like most other sites, which doesn't give it the accuracy or speed that the company aims for. While it might catch wind of a popular tweet at some point, it's unlikely to be snatched and turned into a search result too quickly. This partnership will improve that vastly, allowing Google to show tweets in searches pretty much instantly.
What's not known at this point is when this integration will kick off, or for how long this partnership will last. We'd have to imagine that if after the first year, both companies consider the partnership to be fruitful, then it'd continue. Interestingly, there's no advertising revenue involved here, although Twitter will receive some data-licensing revenue.
One thing's clear: Twitter's CEO Dick Costolo is serious about getting Twitter seen by more people -- especially non-users -- so it's not likely that this will be the last big partnership we'll hear of in the next little while.