What is the profit of folding@home, mersenne prime number search, or other distributed computing projects that people participate in? Even if merely donating your computing, you are supporting Bitcoin's transaction processing and defending the network against attack in a way that just buying Bitcoin does not.

Regarding profit, there is a certain "turn off the miner you already bought" point. This has already happened for CPUs, GPUs, FPGAs and a lot of ASIC miners. It doesn't make sense to pay the power company for BTC when you could just buy them for less. Some miners have contracts or operations with "free" electricity that allow them to operate older equipment, and still others continue to operate their equipment even after they are past break-even.

Bitcoin miners turn electricity into heat, so if you were running a space heater under your desk to keep your feet warm, you might as well have a miner plugged in instead to make heat + Bitcoins.