There's a great article over at Newsfactor about the booming iPhone gray market, it appears that unlocked iPhones (of which there are supposedly as many as a million) are coming out of all sorts of crevices in the standard iPhone market. One big source is apparently iPhones that "fall off the truck" directly from the factories in China. That's not the only way they get out, though, turns out that people are using an incredible amount of ingenuity to grab the suckers for reselling on the gray market:
Sometimes, it is as simple as asking friends and family members to tap out their limit, which for individuals is five phones at Apple and three at AT&T. One reseller admits he got a friend to print business cards and pose as a small business owner so as to dupe an Apple Store manager into letting him buy 100 iPhones for his "employees." - Newsfactor
Buyer beware, though. If you're buying it direct from Apple or AT&T, about the only real risk you're taking is a precipitous price drop right after you buy it. If you buy one on the gray market, you never really know. And for the resellers themselves, the number of people trying to defraud them is awfully high, as well.