1) You use a router anyways.
2) It's always plugged in and powered on.
3) It's always connected to the internet.
What if you could buy a router that double functioned as a bitcoin miner? With, say, 1 GH/s? Would you buy one? How much would you be willing to pay?
I wish I could run a hub of block erupters off of my roku. That's on all the time too =D