Had a great presentation by Shawn Wilden on GridBackup. GridBackup is a friendnet that he's building on top of the allmydata tahoe grid. It's a work in progress, but he's clearly done some up front thinking as evident from his slides.
Shawn's aim is to have the (dumb) end user install an application on their windows/mac/linux box and have it just work as a complete backup system. Sounds like a great goal. It will be fun to follow. Wouldn't it be sublime if a dd-wrt-like firmware included a friendnet solution such as this out of the box?