Not outlawing something because "they'll just do it elsewhere" is just silly to me. Imagine if governments used that same excuse--it'd be anarchy. I don't think theymos wants to ban account sales, scams, sig campaigns, or anything else because those things bring in a lot of money for him, which is unfortunate. And Lauda has alluded to even darker motives, which I don't doubt.
It's so easy to think that members with green trust are OK to deal with without using an escrow. It's so easy to just trust them enough....and then you get scammed, and scammers know this, and that's why they buy green-trusted accounts from the likes of QS et al. I got scammed myself last year, though it hasn't been proven that TimSweat was a bought account.