Should we share our Wi-Fi in the name of cloud?

Novel idea of the day: Allow Wi-Fi routers to share bandwidth with the outside world via a side channel.

Dana Blankenhorn over at our latest addition---SmartPlanet.com---makes the following suggestion:

Give each router its own on-off switch, so that it will remain on after the computer it is tied to is turned off. Then provide software in the router to allocate bandwidth, between the local network it’s linked to and the outside world.

This “side channel” would consist of those bits not being used by the home network. If you’re home and downloading software or a movie, in other words, you take all that bandwidth. When you’re away, however, when the computer is off, that bandwidth becomes available to others.

This is the opposite of what happens now. Right now I can only use others’ routers while their PCs are turned on. I am stealing their bandwidth while they are using it. With a side channel, I can share their bandwidth when they are out.

Sounds great, but I see problems ahead. Firewalls aside, I smell a security risk. Yes, I know my WEP key is a joke, but there's a perception gap at work. 

If enough folks and routers took advantage of this proposal we'd have a Wi-Fi cloud lickety-split. Thoughts?