It’s just harder for Google to find.
Squidoo took a tongue (and Google) lashing for getting overrun with spammy pages/accounts. They’re open to the viewing public and efficient at generating attention from the rest of the internet – it was to be expected.
Facebook is growing like wildfire, and it seems a lot of folks are betting their reputations on it by showering the social network with glory. I say where there’s that kind of attention, there is bound to be someone lurking around trying to find a financial advantage. You can debate legitimate avenues for generating income off Facebook’s back, or you can keep your eye’s peeled for the sleek underbelly already working it’s way in. Some folks already see the latter, and aren’t too happy about it (although I’ll take criticism by the A-list crowd over the chance of someone from the Z-list crowd making some spare coin with a grain of salt).
Yes, Facebook has great privacy features, and it is closed off to the rest of the world to boot. But all that means is if spammers and scammers jump on the platform, it’s the users that are going to have to deal, instead of counting on Google to put the kibosh on it for them.
UPDATE: Even if the barrage that hits you is legitimate, it’s still a barrage. I don’t know what’s wrong with being so “web popular,” other than the fact that if you reject the invitations people will call you a jerk. Guess the price of online fame is bankruptcy.