Just wondering, would a post offering an exchange of goods, for example, a WoW account with 47 hunter+mmoglider elite key in exchange for someone buying me BioShock for my steam account, be against forum rules?

I would guess that while it's not violating any specific rule, that it would be a bad idea to do so.

Selling accounts in games is usually againt their terms of service, so by advertising on this site to try and do that, you're in theory making twp an accessory to it.

Besides, WoW in't worth bioshock. I wouldn't trade the stuff that I find inbetween my toes for a WoW account.