Noonehereyet, you're right in that a bluetooth version of this kind of direct peer to peer filesharing has been implemented, but I was more interested in wifi for the reasons listed above (especially range).
I guess I was envisioning a massive ad-hoc network of android phones much like this:
Self Organizing Wireless Mesh Networks - Microsoft Research but with mobile phones.
I think until a native direct connection for android becomes available the best we could hope for is Radzell's idea of having an android node act as a router to accept connections while simultaneously having multiple wifi connections to other android nodes.
This said, I have no idea if the software exists that would let android phones open multiple wifi connections. As for acting as a router, there may be some apps originally meant for tethering that let an android act as a router.