They're completely and utterly useless.
They're just a way of measuring the value of your trophies - for example, you could have lots of trophies that were for posting your first work/post/Trainer Card and so on, but those three trophies together measure far less contribution to 'Charms than a single trophy for getting 500 Likes, for instance. So the points serve to show that.
There is the obvious idea of "spending" them, or unlocking things on the site once you've hit a certain amount, but none of that exists at the moment, and we've not got any plans right now to introduce anything. ^^