Microsoft under siege?

This article regarding the recent Sun - Google alliance suggests that Google's backing of Sun's Star/OpenOffice freeware should be deemed a shot over Microsoft's bow. The thick client wars are heating up, with the Google team taking the side of a web service model...but that isn't what OpenOffice provides - it is just an open source set of office tools. No revenue for Sun comes from this deal, and no committment by Google to do anything specific. Not that it stopped Microsoft's stock from dropping on its announcement...which maybe was the point after all?