It's not as though could be browsing one day in search of "abortions Chicago" or "genital warts" and have that auto-published to your FB page. You'd have to give an app explicit permission to share activities on your behalf.
A month later, you're Googling for a local STI clinic and have no reason to believe that clicking on the top result (LocalTimes' eclassified section) is going to share your interest in local STI clinics with all your social network. But it is, because LocalTimes' single signon site which you're already logged into makes no distinction about what is and isn't to be shared, but they have made efforts to adopt this revolutionary new form of passive sharing which is going to push up their pageviews.
On another note, I'm seriously considering closing my FB account once and for good and leaving for G+. I have a good crowd of friends willing to do this (and invite their friends), but G+ offers no way to import FB data, which would be a nice feature.
G+ makes as little sense for a private person as Facebook, if not even less.
The bottom line is that what is actually going to happen here in the real world is that people are going to connect their Facebook account to these web sites, not realize or forget (yes, people forget these things) that this web site has been given the keys to the castle to post whatever it wants on their behalf, and a ton of shit is going to get posted to the internet that was beyond the intent of the user originally clicking buttons just to get past an annoying confirmation dialog.
That said, the people fighting against this are fighting a losing battle. Facebook is basically going to control the world unless someone comes in and tries to beat them at their own game and impose their own vision of how and when information like this should be shared.