It would suck down users batteries.

The Cell phone network cannot be truly free. The physical infrastructure has to be paid for somehow.

could be a nice idea, but who will it benefit? the operator or the enduser?

classicsat, the only thing that wouldn't be free is the cellphone itself. yeah, it might suck down the batteries, but they are working on new technologies for batteries as well.. for example: different kinds of super-capacitors are in development).

Cadey, It would benefit the user and the operator (if there is an operator). It would be decentralized and would not require any infrastructure. So the operator would only need to supply the cell phones and the user would hopefully get cheap or even free service (after the cellphone purchase).

How do the cell phones communicate with other persons outside the "network" if there is no fixed infrastructure? What if the phone is in the middle of nowhere, or there are otherwise no like "network" phones available to communicate through?

Maybe those phones could also be plugged in a computer to use VOIP (and then route calls for phones which aren't plugged in). They would get charged up at the same time to incite more people to be plugged in.

If you are in the middle of nowhere you would be out of luck I guess (unless the phone could be roaming using cellphone towers or satellites)... Regular cellphones don't have coverage in the middle of nowhere either even if they could.

When there is already a a battle over minutes usages from one cell company to the other, how would a person who is being used as a jumper be able to protect themselves from having their minutes used up by another jumper? Also, FCC rules specifically say that no antenna source based communication device will use another device's frequency or antenna to hop their signal along to another device. Which is what you are basically saying your idea does. Might want to check with the FCC to see if that can be done.