Mine was hanging off on the Motorway recently! Managed to pull over just in time as when I got out it came away in my hand. Looks like a cheap design to me - adhesive on some clips. Ford told me it is a common problem (admitting the poor quality!).
They had to order me a new one in but after they had fitted it they came out and gave me my keys, forgetting to charge me the £20 they wanted for it! I am expecting the bailiffs any day...