its a good idea but l see one issue, most ppl would have NO gametime on their acc and will say sumfin like " u put in the gametime and then il send in the gold, in which case u have to have a credit card and ul have to put in ur details etc....n then if u scam them things might get kinda messy, if u get my drift (LEGAL ACTION!) but i suppose u cud du the old paypal subscribe and then cancel subscription thing but im not too sure if blizzard can get ur details of it..... well thats just my 2c worth :P>
other than that i guess ud just have to get lucky :P
cheers