It depends where the freezing risk is. If you have a problem for pipes buried in the ground, then any faucet will do. if you have some pipes buried within your insulated walls, then the faucets attached to them should be running.

If you have lost power and the whole house is dropping below freezing, then I would shut off the water at the source, drain the system including the hot water tank (being sure to turn off power to the tank's heating element - it can burn out if the tank is empty), and put antifreeze in the toilet traps and other standing water, as you would when shutting up the cotttage for the winter. This wouldn't be necessary for a short term problem, since it might take several days for the house to cool to the freezing point.