You can buy and sell bitcoins on Coinbase, which is also a wallet (bank). They keep 87% of their funds offline to prevent customers from loosing their funds in the case of hacking.
Yeah, and I know what they are, although I wouldn't describe generating a wallet on an offline PC and keeping it offline as 'very clever'. At any rate, after reading it again I think I confused what the parent was insinuating, so nevermind.
http://howdoyoubuybitcoins.com/from/coinbase/