Originally Posted by
Firewind
Not exactly a direct answer to your question, but fundamental to all of this is that, while they'll take your money "as if" it were a real transaction, you never own the miles/points that you "purchased" according to the companies' terms and conditions.
You don't have to take ownership of something in order to have a legal transaction. Consider renting a car or "buying" software. You don't get ownership of anything in either one. You get permission to use something under the terms of a contract. It's the same with miles/points: you have permission to use them, though you don't own them.
Legally, a valid contract requires a consideration on both sides. Ownership is one type of consideration. It is not the only one.