Currently the tor blackmarkets however only run on bitcoin

Worth noting that a few have tried Litecoin or Darkcoin; today I'm adding to the list a new cannabis market, Diabolus, which claims to support both Bitcoin and Darkcoin.

(However, despite a little dabbling by the black-markets, I don't expect altcoins to supplant Bitcoin anytime soon for them: currently anonymity doesn't matter to the sellers since I still know of no one who has been busted even partially due to tracing coin movements! What they need are ways to cash out, and Bitcoin is king in that respect.)