I feel that it is outright scamming, you aren't supposed to sell accounts and the related trust. While the selling of accounts is allowed, though I think most people in the community frown upon it or don't condone it, but nevertheless it is tolerated by the mods and admins.
The actual act of selling/buying accounts isn't scamming. Depending on how they are used, thats a different story. If people want to use them for signature campaigns... Fine. As long as they follow the campaign rules (IE not muti-accounting it) theres no issue. However, its impossible to tell if they are following the rules or not (Many break these rules). I don't actually believe many people buy accounts to scam, as it just sounds ridiculous. Who would send someone money just because of how high their forum rank is, when its clearly known (even if its not known, its a forum account!) that accounts can be sold/bought. People need to do their own due diligence...