Can't really pinpoint it to one thing. What I was trying to get across was the fact that numbers (P/E ratios, etc.) should only be a factor in one's purchases. I think that when you look at Facebook, the market it is in, and its revenue model, and then compare it to Apple back in 1980, there are some stark contrasts you'll find. Sure, there's hindsight bias and all, but I personally feel that Facebook has entered a market where making money is a lot harder that it was for Apple. In order for Facebook to grow a few order of magnitudes, I feel that there would need to be a radical shift in the way we Internet users feel about spending money online or else the way advertisers reach potential customers.
But I just looked at your profile... and wow! That's one impressive resume! I'd be a lot more interested in hearing your perspective on Facebook and its financial strength, etc. This is one of those moments where I'd really wish HN had a PM system.
Their ad system is going to make them a lot of money someday. I'm going to buy when I see the early signs of them finally figuring out how to bring their ad system up to par with Google Adwords, before the mainstream realizes it. It will definitely get there, it's just a matter of time.