Twitter has given Google access to it's API so now tweets will be able to appear in search results in real time. http://searchenginewatch.com/sew/news/2393959/tweets-to-appear-in-google-searches Google has been crawling Twitter for awhile now, eventually indexing tweets, but now with direct access they will appear instantly which has the potential to have a big impact imo.
For example, when a big news story breaks, how much of the 1st page will be tweets about it? Will brands' annoying habit of "newsjacking" now get taken to an even greater level? Will keyword-optimized tweets become a thing? It'll be interesting to see what changes we'll see in SERPs and just how big an impact having "instant access" to tweets will be for Google.