shouldn't they have their threads locked until the member is back and reports them to be reopened if they so wish?
Case in point - http://www.hotukdeals.com/for-sale-trade/lots-of-dvd-s-game-s-xbox-360-pc-ma/776693
Otherwise you get legitimate threads being bumped down whilst people fall over each other making offers even though there can be no reply. (also possibly encourages OP to sign up as a multi and PM those interested and dealing that way)
Otherwise, where is the deterrent to breaking the rules?? They probably end up benefitting from a bidding war whilst on hiatus.
There should be more done to penalise those who don't follow the rules like the vast majority rather than vice versa.