>>16HTSQL looks nice. It might open DDOS attacks though if peers can repeatedly run expensive queries. The protocol will probably stay restricted to delta updates for the peer communication, and page requests to the web interface.
Yeah, I read the slides on gnunet that were linked here I think. I'll keep this stuff simple though. It'll just assume each peer has a table of addresses of the other peers (which may change dynamically, and peers may come on and off line), and these addresses may be ip addresses or something else like a tor hidden service. Communication among pears is done by TCP for compatibility with tor, and probably anonymity networks in general.
What constitutes a delta update would become application specific. A new post or a new thread on the bbs is published. Friend A uploaded a new photo. Etc. Both binary and textual data should be supported, and compression could be nice. Although unpacking opens up more DDOS attacks, zip bombs, etc. Distbb only needs text, so that is easier.
I'll focus on the functionality first, and worry about plugging holes for spam and abuse later. Maybe spam prevention and malicious peer detection can be implemented at a more generic level than the bbs.