They have a policy of sending the newest DVDs to their "best" customers. Best meaning those that don't turn around DVDs very fast. Since I stopped watching so many DVDs and only get a couple a month, my requests come instantly.
For example I put The Hurt Locker
on the top of my queue on Oscar night and got the "long wait" message. But when I sent in my DVDs (that had been sitting around three weeks) the next day I got it.