I've now seen two Facebook games close after an arbitrary period of time. Plants Vs Aliens and Lucky Train. The first was a rip-off of Plants vs Zombies which is fair enough, but the other game was still making money and was otherwise being casually used by thousands of people. What's common in both is that neither bothered to inform their userbase in advance of the closure, and neither offered to refund customers.

While it's all well and good paying for virtual services, be aware...