Facebook's decision to use people in their ads, and also automatically subscribe people to spam from Facebook Pages, has already made clicking the Like button a 'heavy' action—meaning I have to think about it before doing it, and most likely won't click nowadays.
Google Plus is the same now. I used to consider handing out a quick +1 to any post I liked, or a cool site/service. But now, I have to think about whether I would be okay with my profile being associated with whatever that article/site/service is doing, and whatever they may do in the future.
I've already opted out, but I've now lost my trust that clicking +1 is a lightweight/safe action.
The only social button/action that seems safe anymore is the 'Tweet this' button... Hopefully Twitter doesn't screw that up.