In reply to Jacek:
I went a few years ago and after an admittedly not very exhaustive search for a DIY route/loop gave in and booked a week with exodus. We did an around mt toukbal loop out of Marrakech. I'd never done an organisedy trip before and was a bit turn my nose up at it and it was brilliant!
In terms of logistics / sensitivity to the local villagers whose homes we travelled through / meeting a few pretty keen MTBers who had flown from California and all over the UK and had alot of experience it was a very pleasant surprise what an enjoyable week it was. With a few days eating fish by the sea after in Essaouira it made for a really good trip.
Its an ace country to bike / travel in and well worth the effort. Tip, don't get a massage in a hamman any time before the ride as you won't have much skin left on your back which gets a bit uncomfy!