If I were to buy a used iPhone 4 (e.g. from eBay), which carrier(s) would allow me to activate it without a contract? Is there an activation fee? Anything else I should be aware of?
UPDATE: It seems there is less knowledge as to what Verizon's policy is, and as luck would have it they're my current provider. I would like to know what their policies are also, if anyone happens to know.