First rule of Fight Club is: You do not talk about Fight Club. And that seriously seems to be the case with the not-yet-launched Fight Club feature in Mafia Wars that's we've seen loitering in the Marketplace since early April. That might change soon, though, if these rumors are true.
To put this into context for those who aren't in the know -- since early April, something called 'Fight Club' appeared in the Marketplace, marked as coming soon. Further explanation of this feature simply says, "Earn Victory Tokens from winning Fights to unlock exclusive loot for active fighters!'