I've written at length about this before. All DRM providers will go away at some point, or decide keeping the server running isn't profitable anymore. This is why I convert any digital good I buy, and if I can't, then I don't buy.
If any service providing a game goes down that uses this kind of DRM, I will pirate it if I bought it afterwards. How would it even stand up in court that you are "stealing profits" from a business that no longer sells the thing, especially after you already bought a license with no hard-coded expiration to it?
Indeed. Either that or consider it a rental--because that's all it really is.