IANAL, but it appears as if it's up to the individual merchants who accept credit cards and Bitcoin to resolve any breach of contract from MC, Visa etc, should that occur.
Of course, it might be legal for them to write into the contract that merchants may not accept Bitcoin, but as you said, I'm not sure what anti-competition laws would have to say about that...
Thanks for the reference to the Wikileaks situation update, I wasn't aware their situation had improved. Mind you it did take legal action from Wikileaks before anything happened - but at least here we had a case of a specific organisation being singled out that was able to successful defend itself.
If CC companies attempt a similar stunt to try and stamp out Bitcoin acceptance the question is who would defend Bitcoin? The addition of terms and conditions to service agreements preventing Bitcoin use would need to be tested legally, would it be up to individual vendors to fight this because I'm fairly certain small to medium businesses would not be willing to risk losing their primary transaction processing means for the sake of what is for now a niche method. There is always hope a major player (eg: overstock.com) would be willing to take a stand but it ultimately comes down to the question of whether or not it is determined to be a legal tactic by the CC institutions.
Yep, I think the vendors would have the fight it in court. This is indeed why it's such great news Overstock's now accepting BTC. If it gets to the point where they have an increase in sales with BTC that's greater than the cost of fighting it in court, the credit card companies would be in big trouble if they tried to pull a Wikileaks again. Especially because the Overstock CEO seems to personally support BTC. It might end up like Newegg fighting the patent trolls.
