some other smaller companies do receiving and forwarding, some will even scan the mail you receive so you can view it online and see whether it's junk mail or not - http://www.virtualpostmail.com/
There are mail forwarding services out there already, but they cost money and exist at the whim of private enterprises that could disappear at any time.
I can't help but think that there might be a business idea wrapped up in there somewhere, or at the very least, another product for USPS to offer.