Bing launched a couple days early, yesterday morning and Google Analytics users are confused as to why it does not show up in the search engine reports. The day Google released Chrome, their new browser, Google Analytics supported the new browser immediately.
So why the delay with Bing? Well, Google didn't know exactly what or when it would be coming. It did come a couple days early and now that it is here, Google can begin programming that new search engine into the reports. I doubt Microsoft gave Google an early preview of the search engine and how the search referral strings would work. But now that it is live, Google can begin adding it to Google Analytics.
A Google Analytics Help thread has confirmation from a Googler, Anna, that this will be working shortly. Anna from the Google Analytics team said:
Our team is aware of this, and the required action will be taken soon!
As of this morning, it was not working, but I wouldn't be surprised if it was done shortly.
Forum discussion at Google Analytics Help.