I was actually one of the people promoting integrating ring signatures into DRK, but someone (AlexGR?) noted that one issue is that it renders masternodes obsolete. This is a problem when a significant portion of the total coins is held in masternodes and they would no longer be 'locked up' - i.e. supply shock. It also removes the interesting quasi-PoS aspect of DRK, which might be a powerful economic factor in DRK's value. On the other hand, if the masternodes were retained, then it's an antiquated 10% tax on miners, which (in the long run) would be passed on to users doing transactions.
Thoughts, eduffield and others? The ideal case seems to be to improve DarkSend with another solution that retains the utility of the masternodes.
(In unrelated news, Zerocoin/ZeroCash is releasing a conference paper very soon with significant changes that some of you may be interested in.)
I had the exact same thought, but Masternodes are also going to be the private I2P relays. So there's that at least. They have a lot of potential outside of the coinjoin aspect. Decentralized exchange, decentralized marketplace, whatever else Evan thinks up.