Robert X. Cringely wrote about this case back in October:
One huge issue in Burst v. Microsoft is missing e-mails that should have appeared in the discovery portion of the case, but didn’t. Burst knows there are lost messages because many of them were to and from Burst, itself, so they have their copies. But not only are the known messages lost from Microsoft’s e-mail archive, so are any messages on the same subject that may have been sent between the Microsoft people, themselves, and not shared with Burst — messages that Burst only believes to exist, but it’s a pretty fair assumption that some such mail did happen. I have written about this before, and it plays back to a haphazard corporate e-mail retention policy at Microsoft that seems to conveniently lose any damning evidence.