Social sites are not just games or freebies. They exist based on the premise that they can use human nature against itself in order to create free content from users to be consumed by other users. At the end of this road we have Facebook, where they spend tens of millions of dollars to program users to create and consume like you'd program an alarm clock.
The spammers of course are in it for nobody but themselves, so it's tough to ding them any more than the rest of folks. At least most of them seem honest about it.
There's a third party here too, though: the honest internet citizen who likes creating and sharing content and making money while doing so. They don't run bots and they actually review the stuff they talk about.
The spammers make their money because they can "fake out" the system to think they're the honest money-making folks. The danger here is that we're going to only end up with two giant contenders, the addictive social sites and the spammers. That the little guys get crushed. To me it seems that the web, once wide open, is closing in bit by bit. (That probably sounds hyperbolic. Apologies.)