My colleague Alan and I were chatting this morning about Facebook, Microsoft and Google, and it spurred some thoughts about the future of these three companies, and who will win the fight for platform dominance.

Microsoft’s dominance over the past two decades has been a product of its success in tying users to Windows through the desktop. Google’s emergence over the past half-decade draws its foundation on its dominance in search, and its subsequent ability to filter people from search through to external sites, i.e. the Webtop. Facebook now adds the Socialtop – leveraging people’s willingness to share information and communicate online into a potentially lucrative advertising model.

But the question now emerges of whether this latter iteration of the platform, i.e. the socialtop, has the legs to survive on its own. Or more poignantly, is its survival dependent on its integration into one of the other two forms of platforms – either the desktop through Microsoft or through the Webtop and Google/Yahoo!, etc.

Evidently Google’s plans with OpenSocial signify their move in a different direction, but it also provides a relatively phenomenal opportunity for Microsoft to aggregate the desktop and socialtop into one big ‘ole lifetop that merges work and social. Sure there are a few curveballs that could change the environment, aka. Yahoo! / Linux / open systems, but I certainly think that the opportunity is there for Microsoft to make a major move and try to leverage its initial advertising deal with Facebook into a deeper, long-term platform merging commitment. On the other hand, Alan argues Google’s investment in players like Neven Vision (which owns more facial recognition patents than anyone), keyhole, real world display ads, and now their mobile platform play (Android) they might have an edge on MSFT for real-world integration… potentially an important part of the “lifetop”.

So who wins? You tell us.