Official ones too, but I don't know if they do it as often as cheap ones. Maybe that happens more often on cheap batteries, but maybe that's because they're so cheap that you get several.
I have 3 cheap batteries for my N810, 3 for my (to be replaced by N900) phone, bought on DX, I've been happy with all 6 of them. The original battery of my phone has become worthless, that's why I bought them in the first place. They don't hold as much of a charge as the original ones when they were new, but they're pretty decent.

Don't forget that even official batteries have a limited lifetime.