@dixon_jones, a well known and respected SEO, asked Google’s JohnMu in a Google Webmaster Help thread why Google shows the old Twitter URL versus the new Twitter URL in the search results.

For example, my old Twitter URL is twitter.com/rustybrick but the new style for the Twitter URL is twitter.com/#!/rustybrick.

Yes, Twitter uses the new AJAX schema for the URLs. So why does Google show the old version without the #! in the URL?

JohnMu explained because Twitter redirects the #! to the old URL.

Google crawls AJAX URLs using the AJAX-crawling scheme which results in the URL looking like this instead http://twitter.com/?_escaped_fragment_=/rustybrick. When you look at what Twitter does when you access that URL, bots are redirects to the old URL.

Forum discussion at Google Webmaster Help.