There was some controversy about Bungie not being able to show what they're working on at the E3 2008, because of Microsoft.

Bungie posted a statement on their site that they are very disappointed about not being able to show what they're working on to the fans.
The LA Times reports now why Microsoft held Bungie back. Apparently the E3 2008 briefing of Microsoft was initially 150min. long, which is way to long for us journalists to keep alert. Also Microsoft's Don Mattrick says that the Bungie's Halo news would be done more justice with a more dedicated event.

Even without Halo news Microsoft pulled off the most interesting E3 2008 briefing of the big three.
More E3 News.