I found a used 4S for cheap – suspiciously low price, in fact. Plugged in serial number on Apple Self Service and it showed that the "device has been replaced". But the phone is still in use, running iOS 5.01 and baseband 04.08.11. Haven't had a chance to personally inspect the phone yet. If it helps, I plan to jailbreak the phone after I get it anyway – can't live without SMS+, notification toggles etc. Talked to the seller about it and he acted innocent – said it was a gift from his sister in USA (I'm from India). I don't buy it, but it isn't a stolen phone either (or at least not blocked yet). My question is, is the phone a ticking time bomb and possibly blocked in future? Should I meet the seller and inspect? Or not bother at all if there is any risk involved. Update: Partridge, below, links to an an article by an Apple tech support about Apple denying phone support and warranty for phones with replaced status. I'm in a different country, so neither is applicable anyway, but if I take it to a store for repair and am willing to pay, will they deny it on grounds that it doesn't have an active serial?