Enigma

http://enigma.media.mit.edu/

http://enigma.media.mit.edu/enigma_full.pdf

> Are there any experiments with incentivized distributed hash tables? eg. nodes could be paid bitcoin or something for servicing the network.

http://filecoin.io/ is supposed to be this, but it hasn't been fully implemented yet. http://ipfs.io/, which is the generalized DHT framework without the incentives, is fairly functional at this point.

There's also MaidSafe-Routing / Safecoin, which is production-ready.

https://www.youtube.com/watch?v=YFV908uoLPY

https://github.com/maidsafe-archive/MaidSafe-Routing/wiki

I'm the author of TomP2P. We are currently working on integrating bitcoins for registration to make Sybil attacks much harder: https://github.com/tomp2p/TomP2P/tree/bitcoin