Lets think about this for 1 second
1) I don't care how many people +1 something, I care how which people I give a shit about (them and their opinion) +1 something. Those people don't have Google profiles, therefore this is not useful to me.
2) This is incredibly easy to game. So if it has any effect on rankings, or anything else, it will be abused to the point of uselessness.
3) Ultimately this is just about Google trying to get more information about you in order to personalize more shit for you. People won't see it that way, but thats all it is.
4) Like's about are sharing, because of 1) above , you aren't actually sharing anything with anyone that matters.
5) There is no reason for a webmaster to incorporate this other than to suck up to Google.
Again, this is stupid shit. Google can put it on all their toolbars, in all their chrome notebooks, and in android. Other than possibly helping their search results (but not in a way that seems obvious to users, like the like + bing integration where you actually see pictures of your friends) users will see no direct benefit from this and no incentive to use it.
So long as Facebook owns identity, Google cannot win this fight. Google's best chance then is Android to control more identity, but they are so far behind that at best they can own some mobile identity, and never majority of web identity.