It would appear that Microsoft thinks that the FOSS world that spawned Linux suddenly owes Micro$oft a huge amount of patent monies because so much of "Microsoft's innovations" have been "stolen".
Amazingly, Ballmer is not specific about which M$ patents have been violated (which is starting to sound amazingly like the infamous SCO Lawsuit).
While this is mostly a reiteration of various threats that M$ has made against Linux in recent years, should Microsoft actually attempt to litigate this they would turn themselves into the next SCO lawsuit. As SCO has proven, alleging infringement and actually proving it are two very different things - and so far SCO hasn't been very successful.
As for Microsoft demanding license fees for the "infringed upon patents", well, they'd have to identify who did the infringing, and then sue them in court - that could be a rather difficult proposition when FOSS developers tend to be all over the place, and not just within the United States.