Patents in an Open Source World

An interesting article by Lawrence Rosen about patents and Open Source. While he brings up some very good points, he seems to miss one key issue. From the article:
“Don't be too paranoid about the patent problem. It's a real problem, but not a catastrophe. Any patent owner that tries to assert its patents against open source software has many hurdles to leap before the royalty checks start to arrive.”
The part missing here is that some of the patent suits against Open Source may not have getting a royalty check as a goal at all. If you look at the motivation a company like Microsoft would have in bringing a patent suit, it wouldn't be in the additional revenue that the royalty checks would bring in. The motivation would be in scaring companies and slowing down the adoption of OSS, which it eating into their revenues. Luckily, MSFT's first attempt at this with SCO has become a laughable issue, but what if their next pawn is not so incompetent?
–jeremy