If you mine Bitcoins, whether it is for the upkeep of the Bitcoin peer-to-peer network or just for pure profit, you've no doubt got a big interest in the Bitcoin system and/or currency.
Proud of your Bitcoin miner status and your involvement with the potentially revolutionary peer-to-peer crypto-currency? Perhaps you want a t-shirt to prove it, show it off and perhaps even promote Bitcoin itself a little. A 'Bitcoin Miner' t-shirt is certainly a good talking point and possibly a neat way to introduce new people to the currency.
This could be a good t-shirt to wear during any Bitcoin related meet-ups and/or conferences.