That point does stand, however the situation would be different. When you think about it, right now there is nothing stopping you from involving in these trades (there are no 'risks', apart from possibly getting scammed by either the buyer or seller). In the case where account sales were disallowed (a bannable offense) there would be no more sales on the forum (they'd have to try to engage in these trades somewhere else) and now a certain risk factor would be present (anyone who gets caught doing account sales would be permanently banned). This would reduce the amount of trades by a noticeable amount.