1. Banning the sale of accounts is no different than banning the sale of crack, guns or CP in the same subs. Those are already verboten in those subs, and the mods aren't dropping from exhaustion.
Selling of accounts would just move to places outside this forum. How would you want the mods to crack down in that case?
Why do you want it to happen on the forum? Any specific reason why should Account Selling be allowed here? To me there's just one reason that people Earn Bitcoins by doing so and hence they want it to happen. Nobody cares if people spam the forum by owning many accounts and scam members.
If people move outside the forum and find any other means, they will be banned as this would be against the rules. I don't see any benefit to the bitcoin community or the forum by letting this happen.