Amazon iPhones?

Okay I've been looking into getting an iPhone 4 with no plans of having a contract for the next couple months and basically kind of using it like an iPod until im ready to activate it, and I don't really want to buy the phone straight out without a contract from a store like Verizon or Best Buy because the prices are crazy, so I saw the iPhones on Amazon which are reasonably priced (around $200) and you just activate them whenever you want, but I saw a few bad reviews for the iPhones on Amazon and all were pretty much about the same thing, which was that the apple stores were telling them that the phones were fake or they had problems with keeping a charge on them? were these just coincidences or have any of you purchased an iPhone off Amazon and had similar or different problems with it?