Follow means "subscribe to our feed", Like means "subscribe and upvote", +1 just means "upvote". Google's had similar verbs in terms of interface (stars/bookmarks, SearchWiki voting, likes, etc.), but they weren't public. The SearchWiki announcement emphasized, "The changes you make
only affect
your own searches." [0]
reddit, HN, and StackOverflow have only scratched the surface of can be done with upvoting. I would very much like to see Google add a prominent "+ Average", like HN's comment score average. As we've seen here on HN, focusing on total upvotes (i.e. the now hidden Leaderboard) seems to encourage quantity of comments, while displaying one's average may encourage quality. Facebook and Twitter are clearly optimized for quantity; the best hope for Google+, hopelessly behind in terms of sheer content, may be to push users to generate/share more interesting content, rather than more.
[0] http://googleblog.blogspot.com/2008/11/searchwiki-make-searc...