I've been wondering the same thing; what are these charms good for?
After reading this thread I decided to burn them on Battlestones and take the chance to get some of the green non-wild pets blue.

I do all Pandaren tamers + spirit and usually get 1 per day. Some days I get 0, one day I got 3 but roughly one per day average I think. Only ever gotten 1 from fighting wild pets and that's levelling 5 pets from 22-25 in Valley of the Four Winds fighting mostly level 25 pets. So the droprate from f...

Ah yes, it all makes sense now after reading your posts and having played Pet Battles for a few days. I know see the benefit of having multiples of the same pet - for example you could build a team of 3 of the same pet but have them using different abilities. And also that the skin is different make...

I can totally relate to that, I don't really see the point in having more than 1 pet of each. I guess it's to encourage trading?