His job isn't only to turn up for games though, his job is to work hard all the time so that when the time comes, he'll be in top competitive shape. Sure I've gotten drunk in the middle of the week, but I wouldn't do it if my job required me to be in top shape physically.
Yes, a little R&R is good for a player, and maybe i'll be proven wrong if he comes back and immediately hits top form. But with an important run of games coming up, I would have appreciated it if he took the opportunity to work extra hard, since he can rest over the weekend. Maybe he could even pop over to the beach and have a few cocktails after training, but in that picture he looks sloshed... doubt he's dragging himself out of bed for an early training session after that.
I get the points that the club gave him permission, I just wonder if they would do the same had it been one of our less obviously talented players? I also wonder how much Fellaini is able to get away with, and if his importance to the club may come ahead of the tight ship Moyes likes to keep.