This has happened to my iPod too, but my + volume button is also broken so it's really quiet and I doubt there's any way of changing that. Apple being apple will obviously only replace it if it's under warranty despite the fact that this clearly a design fault.
Also, for those of you who are saying "this iPod sucks... NO GAMES QQ" I'm going to explain just how wrong you are. This iPod was in no doubt a step in the right direction. The last iPod had games and various other pointless pieces of software which I didn't use once. If you want an iPod that you can use to waste away money on games which you'll use maybe a few times BUY AN IPOD TOUCH. The 6th generation nano is purely for music; it's conveniently small yet its functionality (Other than the hard button on top anyway...) is brilliant. Incredibly useful for running/fitness etc.
So, yes, Apple are doing it right. They're making each of their products individual compared to their other products. So kudos to Apple for that, I just wish that they had more official shops instead of the fake ones that won't actually repair my iPod, warranty or not...