Here's what Google said with regard to its disappearing Twitter feed: “Since October of 2009, we have had an agreement with Twitter to include their updates in our search results through a special feed, and that agreement expired on July 2. While we will not have access to this special feed from Twitter, information on Twitter that’s publicly available to our crawlers will still be searchable and discoverable on Google. Our vision is to have google.com/realtime include Google+ information along with other realtime data from a variety of sources.”
For now, Google's Realtime Search URL returns a page not found error. It's good that it's revamped Realtime Search will include more than just Google+ results since until Google+ is available to more people it's going to be lacking somewhat in content.
What's interesting is that Bing has a similar deal with Twitter. That service, Bing Social Search, is still working, and still more interesting is the fact that the Bing and Google deals were announced on the same day, yet Bing's is still in force.
That said, the timing of the "outage" is interesting. Google recently launched its Google+ social networking service, and although invites are few and far between, it's definitely a rival of both Facebook and Twitter.
Google has gone so far as to tie 2011 employee bonuses to its success, or failure, at social this year.