Mobile Communities/Social hubs

Hey all,
I'm looking into trying to set up a leaderboard/achievement thing using a third party service like Gree. Sadly, the only one I've been able to find that works across iOS and Android is Gree. Is it common to implement a social hub for each platform?

And what does the unity community consider to be the best services in the area?

As a pre-emptive thank-you, here's the oddest jpop song/video I've seen in a while - http://www.youtube.com/watch?v=yzC4hFK5P3g