A good point, but I bet those on eBay are ones purchased legally and being resold at a substantial premium. This site purports to be an online retail store selling iPhones at retail prices, so where did they get them? Apple’s ordinary resellers (e.g., MacMall, MacZone) don’t have them. Search Google for iPhone Stores and you’ll get a bunch of links for Apple sites, AT&T sites, and iPhone accessories sites.
The only thing that appears legitimate about the site is that the iPhones are priced at $5.00 off retail, which is pretty routine on legitimate sites for other Apple products.
I’d be very careful until someone confirms they actually purchased a phone successfully from them, and were able to activate it through iTunes with AT&T.
As an aside, as of yesterday every Apple retail store still had iPhones in stock, so unless you live in the boonies there’s little reason to purchase one online.