Isn't it just a matter of time before the cost of electricity becomes higher than the value of mined bitcoins?
I think is true for many "older" (use the term lightly) miners, but if you look at the new hardware coming online now, it is not only faster but much more efficient....
Example:
BFL 10 GH/s cube (still for sale, but who is buying these things???)
Price: $349
Consumption: 3 to 4 Watts Per GH/s Per Chip
Antimer S1 180 GH/sPrice: $400
Consumption: ~2 Watt Per GH/s
Antimer S2 1TH/sPrice: $3,599
Consumption: ~1 Watt Per GH/s
Spoondoolies-Tech SP30 Yukon 5.4TH/sPrice: $11,995
Consumption: ~0.38 Watt Per GH/s