no, i think you are correct.
This forums allows M$ the possibility of logging on as users and saying inflammatory (or other) things, also it is a handy, easy and cheap way to monitor the trends amongst a certain subsection of computer users.
By reading this forum, M$ can effectively augment their statistics (gathered using the 'phone home spyware) quite effectively, since the people here are representative of the slice of the market who beat the spyware.
Any publicity is good publicity like you say.
The only way that this site could ever actually threaten M$ is if M$ become complacent. i think this is happening already, but let's hope they are too complacent to take me seriously, assuming they are reading this, because if they heed what i say, they may take anti-complacency measures and then (oh irony of ironies!) i'll be partly responsible for the survival of Microsoft!!!