They don't need cookies to track you when your browser footprint is unique enough (http://panopticlick.eff.org/).
So you still need a tool like Ghostery (http://www.ghostery.com/) to disable the snippets that can track you.
But then again: when everybody is blocking Google and Facebook, how would they earn there money?
I think that endgame is obvious, they bribe users to let them track them.
Information about TV and radio habits is very lucrative for companies like Nielson -- they pay quite well for participation and diary keeping. Even taking short surveys over the phone is rewarded with $25-50+ checks.
A company like Google is in a unique position to automate this process -- opt in to tracking and receive a tiny percentage of the more lucrative ads google is able to get. Win-win, tell your friends and almost everyone signs up.
Assumption: targeted advertising is more lucrative than indiscriminate advertising. (I'm not sure this is true, but it seems to be accepted common wisdom.)
If I were to run FB or Google, and discovered ads of any type were being blocked, I'd naturally try to change the minds of my users the old-fashioned way: money.
The problem is the entire "free through advertising" model. Once you set the price of something as "free" (ala Gmail/Google search) you have a tremendously hard time charging people for it. Sure you can provide "premium" features (ala the freemium model) but how can you do that with search?
But then again: when everybody is blocking Google and Facebook, how would they earn there money?