1. Any user with a PC or Mac can back up copies of their paid applications, and should be able to. This is the problem because of #2 below.
2. Paid apps are not tied to any unique device identifier. An app I pay for and back up can be sent right to you for installation on your phone. If the Android platform fails (and by fail I mean shows little to no growth) it has to be partially because of this.
Solution? I have no idea, but I'm sure that an app could be checked against the phones market account every now and then to see if it's been paid for.
My solution? Teach my kids that stealing is wrong, and a man deserves a bone for his hard work...whether he's a plumber, a doctor, or a programmer. It takes quite a bit of 0.30$ profit after carrier fees to put a loaf of bread in a mans kitchen.