(Sidenote: Google search is not just PageRank. Many of the recent changes to search require more than just a better popularity metric. Obvious things are things like better stemming or stop wording which are quite tricky to get right.)

possible, but that would be one hell of an epic court case. probably wouldn't even be worthwhile to try and jump into that. both sides would probably lose a lot, on multiple levels.

Yes, I was thinking PR. Odd fact: Yahoo appears to have a license for PageRank (Yahoo bought overture/goto, whose patent Google infringed with AdWords auction). GOOG-MS might cross-license too.