Silk road, lmao. Seems an easy way to set up a sting to me. Anyway....
The guys at work are 'mining' these things with their home pcs (and to some extent, the works servers i suspect, tut tut.). You basically use the power of your pc to solve an SHA-256 algorithm block, for which you get rewarded in bitcoins. The faster your rig, the more bitcoins you get. PC GPU mining is about dead now (due to hashing power difficulty rising over time) but FPGA and the newer ASIC mining rigs can still have you churning out a profit. The more hashing power you have (measured in mega hashes and giga hashes a second - mh/s, gh/s) the more bitcoins you can generate.
Now, imagine a wind turbine 'off grid' setup with a bitcoin miner plugged into it. Money from fresh air my friends!