In reply to Ice Nine:
Just returned from Tafraout. I got an inwi SIM at the airport last year and managed to top it up at the airport two wks ago. However, when the data ran out, i couldn't top it up with my credit card on the inwi website. So i abandoned it.
I bought a new one (30 MAD) from a shop in Tafraout, (on the square by the Salama) and bought a 6 GB top-up over a month, for 50 MAD. Worked fine.
Another member of our team bought a 1 GB top-up from the same place, only to find that it stopped working after a week. I suspect you had to use it within 7 days. Ask the guy how long it lasts, a few days, a week or a month.
Coverage is pretty good out there. One of our team even answered a few work emails on a belay on Rainbow Buttress, at the top of the Samazar.