I'm at an apartment so it doesn't matter if I use $1 of electricity or $10000 of electricity. But I think the wear to my rig would still cost more than the $3 I might make.
Incidentally, CoinLab will soon be releasing a client that performs scientific computing work and pays out in bitcoins. An NVidia actually performs better than AMD GPUs for this type of work. Currently they only are doing a bitcoin mining pool (95% PPS) but "soon" for the HPC client.
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http://bitcointalk.org/index.php?topic=99643.0