Which is great when it works the way its meant to-- I'm always annoyed when I find a "Scrap of Paper" taking up a slot in my bags at 55 from a quest I'd abandoned twenty levels ago. But according to what players are saying, the destruction is a little on the greedy side-- it'll even destroy items you've picked up for the quest, i.e. if you've looted Arugal's head and then abandon the quest, bye bye to your head. And I haven't yet heard what might happen on normally non-quest items-- if you have 6 stacks of runecloth in your inventory and a quest requires 3 pieces, will you lose everything when you abandon it?
It doesn't help, then, that this is mentioned in association with "curbing experience hoarding." A lot of players have already put quite a bit of work into saving up turn-ins and otherwise to quicken the route to 61, simply because they weren't told before this that it wouldn't be allowed. And especially if this "functionality" causes people to lose things they don't deserve to lose (or just plain want to keep), the fact that Blizzard did it (in only part, admittedly) to slow down player progression might be pouring salt in the wound (did they even put an "item destruction imminent" warning in the abandon confirm?). At any rate, be careful with your quest items when abandoning. Anyone tried trading them to a friend and back while you press "Abandon"?