Aren't most who sign up just going to add to their Bitcoin collection and Hoard them as well, wouldn't it be better to set up number of online shops to encourage real trade.
There are all sorts of ways to promote bitcoin use, one being what you've mentioned. We're just doing it in a fun way that will make some people very happy (it is probably not the best way to spread bitcoin but perhaps others should join in and set up their own little projects!)