I think he's right to question the viability of the brand. Facebook has accumulated a pretty incredible amount of unflattering connotations over time, and is now probably one of the least cool tech companies around, at least in the eyes of normal people. Personally I find it telling that the people I respect the most are those that publicly post on Facebook the least (naturally I use it post publicly never :) )
The danger here is that once a company gets uncool, they often get desperate to try and prove that they're cool again. For an example of how well that tends to work out, see Microsoft's increasingly-shrill efforts to prove that they're still hip. The problem as far as I see it stems from the fact that the best companies project an image of selflessness - they're not actually trying to make money, they're just people who have a really, really amazing product, that they love so much, and are so happy introducing to the world. Once a company gets uncool and desperate, and starts casting around trying to reinvent themselves, they are basically openly admitting that their only purpose is to make money and their only desire is to beat their competition. This is Microsoft's position right now, and it's not tenable in the long-term in my opinion. People just don't like desperation and the dishonest posturing it breeds. Facebook could walk right into that same trap (not helped by the fact that Mark Zuckerberg is so uncool.)
No. Based on everything I have seen or heard of him in the media, including videos of him in speaking or interacing in social situations. He seems extremely awkward and completely bereft of charisma. The polar opposite of Jobs.