I do agree that getting into Bitcoin mining, even as a business, is very risky. While philosophically, Bitcoin has definite strengths compared to existing currency, it also possesses unique weaknesses. Even if it is on the right path, it may not be the final destination, which adds further risk. Still, if you're able to mine now, with what you have, it shouldn't hurt you. Another $20/week in pocket change probably deserves a "Why not?"
OTOH, the total BTC economy is extremely small. Should it grow, in particular in spite of the efforts of parasites (i.e. government officials), each BTC could conceivably end up worth a considerable amount. I wouldn't invest "real" money in it, as I'm rather risk-averse. Still, if the limited BTC I can get by mining do nothing more than offset the cost of a powerful graphics card that's great for games, I haven't lost anything by doing it.