My opinion? If you're hoping that your members will go out and promote your site... if it's blatant advertising, I would probably say no... especially if visiting your site is something they do in the privacy of their own home. BUT, if you come up with something that someone would wear out just for the sheer entertainment/reactionary benefit... you can advertise the site as an afterthought... I guess my point is, it's all about the hook. Subliminal advertising....
OR, if you attend the trade shows, use the industry to promote your site for you - these are the people that will wear your free shirt... there were some GREAT ones flying around in Florida.
