- http://www.foxbusiness.com/personal-finance/2012/07/16/settlement-allows-retailers-to-surcharge-for-credit-card-use-will/
I can see merchants doing that and finding lots of their customers start paying with paper money and coins and learning even that isn't the ideal situation either. There indeed seems to be a place for bitcoin here.
This happened in Australia years ago and in practice there are very few businesses which add the surcharge. This is possibly because interchange fees were reduced at the same time and merchants now receive the money from transactions in their bank account within a couple of days, so they're ahead financially even if they don't pass on the cost to the consumer.