Dubai is another junk-bond market that is being dumped on amateur investors, complete with guaranteed rental scams and all the usual garbage that makes the pros run a mile.
Bottom line, something like 15% of all the world's cranes (to give you an idea of the sheer size of the bubble) are engaged building so many apartments and villas in Dubai that the market is bound to implode when they are all finished. If you increase the housing stock anywhere by a multiple of 200 times, what do you expect?
Also remember that most holidaymakers in Dubai go to hotels, not to apartments, and this is unlikely to change anytime soon. Add in the cost of fuel, for transport and airconditioning in temperatures of 50+ degrees, as well as the fact that your title is dependent on the whim of the local sheik, and you begin to get the picture.
Roll up, all you gullible idiots with more money than sense.