In an interview with Forbes... Microsoft’s CEO Steve Ballmer stops short of announcing patent litigation against Linux:

"Well, I think there are experts who claim Linux violates our intellectual property. I’m not going to comment. But to the degree that that’s the case, of course we owe it to our shareholders to have a strategy. And when there is something interesting to say, you’ll be the first to hear it."

This is almost like announcing that there will sooner or later be an announcement of Microsoft starting patent litigation against Linux vendors and/or users.

Florian Mueller | Forbes Article