Tenebrix network is flaking on me presently. Fairbrix seems stable, though. Who's mining these coins?

No problem, the dev says about 1.5 mils of the premine are set aside to help recruit developers and sustain support for no less than 6 year. Unfortunately he was last active on August 10, 2013. Things don't seem to have changed much since Tenebrix was released.
Q: I heard you premined, you bad bad person...
A: Well yes, I premined 7 million coins. Why so many - well, to be completely blunt and honest, I got a bit tired of a discussion of how much should one premine that I had going on and used the premine value from GeistGeld. Perhaps not the wisest decision, but worry not though - I will use 2 millions do fuel verry slow (no more than 4 TBX per user, may get less if their price rises) faucets with strong user ID (Google Acc + captchas), and about 1.5 mils are set aside to help recruit developers and sustain support for no less than 6 years (you gotta agree that it is a looong road and a lot of money-gulping things can happen)