Family returns from vacation to find home flooded, frozen

Opening the faucets isn't going to do anything useful to keep pipes in walls from freezing and bursting.

Turning off the water supply is probably the most important preventative measure. It at least means that a broken pipe will not cause an unending stream of water flowing and flooding once it thaws. This is the difference between a mess and possibly a complete loss. It's also good advice even if it's not freezing weather as leaks can sometimes come from causes other than ice.