The way I see it, the Frag Fest section is more for game discussion, not trading. Josetann had an overwhelming supply of topics about people selling their RS accounts, and made them a section of their own. If there had been a ton of habbo trades, habbo would have its own section, though i've never even heard of habbo. If there was a section for "Other Game Trading" or similar, then it would go there, but the RuneScape For Sale / Wanted section is basically a section for trading accounts and items for every game (other than WoW, which recently got its own section).