It is. It's a common misconception that peer-to-peer is only about making the handshake symmetrical. Equal contribution of resources is the important thing. In the case of most peer-to-peer technologies, this contribution is in bandwidth, storage space, and tiny routing computations. In the case of seti@home, the contribution was cpu cycles.

http://www.amazon.com/Peer-Peer-Harnessing-Disruptive-Techno... has a chapter on Seti@Home.

For those not already running it, please install folding@home on your desktop computers. http://folding.stanford.edu/