There should be a list of banned BM cards, because this is just silly.
I don't always play physical games with Black Market...
...but when I do, I make sure the Black Market doesn't contain
Cultist
Fairgrounds
Fool's Gold
Knights
Magpie
Page
Peasant
Peddler
Port
Rats
Tournament
Transmute
Treasure Map
(This list is probably not exhaustive and will probably increase tremendously with Empires. Also, it is meaningless until I actually get a Black Market.)
I'm moving this discussion here since it's probably more appropriate.
My thoughts about a possible ban list:
Tournament in the BM can be really annoying. 100% agree on banning.
I think that the some of the worst black market offenders are vp-token cards, since they create a virtually infinite pool of vp for only one player. So I think I'd ban Goons, Monument, and Bishop. But after Empires, vp tokens might become so common in games that this won't be a problem any more, assuming it's a problem now.
Attacks are really annoying when in the BM, in particular junkers if they have no relatives on the board (Witch without other cursers, Cultist without Marauder). Trashers and hand attacks are ok I think.
There's a case for banning Tactician: Tactician-BM is fun and everything, but combos involving Black Market tend to happen often due to the size of the Black market, and banning Tac would not curb it, rather make the combo more rare and availlable to everybody when it happens.
Dud cards in the BM are fine, it's not like BM needs buffing anyway. So I'd keep all the little Pages, Peddlers, Fool's Golds, Magpies, Ports, and such. I see no reason at all to ban Peasant (except rule clarity issues), since its +Buy might be what you sorely need sometimes. We find that Treasure Map is hylarious when in the Black Market.
Rats is probably ok, since it's just a cheap Junk dealer. It becomes a very different card but not a radically broken one (like Tactician arguably does). Compare with Ratcatcher and Raze, who are not mandatory trashing and are cheaper.
My list tentatively includes:
Tournament
Tactician
Cultist
Goons
Monument
Bishop
(my list is also mostly meaningless, until I get my own physical copies of Cornucopia, Prosperity and Dark Ages - I do ban Tactician)