First the Ballmer video at Web 2.0 Summit. I was anticipating him jumping up on the couch to profess his love for Mark Z. Jeeze! I would love to be a fly on the wall during a Ballmer/Zuckerberg meeting. "Hey there little fella, cmon on in to my big castle for some cookies and milk. Dora the Explorer will be on in a few minutes". If Google is a tween in Ballmers eyes, then Facebook is the real toddler.
In my opinion, the MSFT/FB deal will hurt FB in the long run. When you're a cool company with a cool product and you've been working out of your "garage" to get it built; you grow a certain following. Look at the Google & YouTube stories. Everyone loves those because it shows that garage built companies can be successful, BUT, when the folks that follow, use and understand your new flashy product start to feel that what they love has jumped the shark, they begin to lose interest.
It only takes one event to completely change a users mindset and getting TOO big will do that. $15B valuation, business user base growing and now a partnership with MSFT. Any of these could be the change.
Could this be the start of the end? Only time, and user hits will tell.