Listening to Mark Zuckerberg yesterday at W2Summit was fascinating.  First, I have seen Mark’s performance on stage go from awkward and tentative three years ago to assured and compelling now.  Second, it couldn’t be clearer that Mark is singularly in control of Facebook and aggressively building an organization that can deliver at top speed and scale.  Third, Mark’s ambition and sense of what’s possible for Facebook are huge.  He is very clear that getting to 500 million active users is just the beginning.  Fourth, Mark’s vision of everything we do online being “socially enabled” (which for him clearly means Facebook enabled) has the same clarity as “a computer on every desk."  That of course was for many years Microsoft’s vision.  And so I came away from yesterday’s session thinking that Mark will be to the Internet what  Bill Gates was to desktop computing.  At the same time I was struck by how I don’t have much of a sense these days of what Larry Page and Sergey Brin are thinking and how engaged (or not) they are in Google’s fate.  That is a bit worrisome as it reminds me of what happened at Yahoo.