Top ten in WHAT?! No one uses Google Plus since it came out. It has no advantages over Facebook / Twitter, and I think really is having a hard time finding its niche.
It's fine to be a late player to the game. Facebook came out when MySpace was on top. Google came out when MSN/Yahoo!/Ask were on top. The trick is not to enter the arena just for the sake of having a stake in the game. You really need that great unique idea, which Google Plus just doesn't have [yet].
It takes long to be top. People were so crazy when Google+ was launched. This was the reason that many of them joined Google+ and the news has been passed that Google+ got millions of followers in just...days! I think most of them would be Gmail users who do not needed to register into Google+ and I believe that the profile of google account give the Google+ huge joiners.
well, i have made my account in it and using it since 2 months, but there is no such activity enjoyable, i have found no charm in using it. May be in future it can flourish but rite now it has nothing else.