Both account sales (multi accounting included),and campaigns should be straight out forbidden.
While we may be able to enforce a signature campaign ban (at least to a reasonable degree), I don't see how we could enforce a ban on account sales. We could however, make it bannable and thus more risky for the people who engage in these trades (issue a permanent ban for both the seller and buyer).
How? Bitcointalk does not know when an account is sold.
The best that one can do is determine whether it is probable that an account changed hands.
Since Sr. members and higher accounts are more prone to be trusted and do scam.
A common misconception by ignorant users. There is zero reason for one to trust an account by default just based on their rank.