I'm always interested in adding to my T-shirt collection, but as with the jerseys, price is going to be the main consideration here.
Even if the jersey idea turns out to be viable, the T-shirt would still be good, because some of us do spend some time away from our bikes and the T-shirt would allow advertising the Forums during those deprived moments.
Also, I ride in T-shirts, since I don't (yet) possess a jersey.