"Berlin, last August (2013). My BA Chase C&S was rejected by the restaurant's PoS terminal. Chase.com had no fraud alerts"
Not indicative of anything. Sometimes, time differences, communication problems, etc. cause these things to happen and your bank has no record of any attempt to authorize. If, it is true, then it behooves mc and visa to set standards for the produces of pos terminals that they must accept all valid cards (I know that's the rule right now but rarely enforced). Then they have to enforce the rule. So mc and visa can, for example, fail to license any manufacturer of pos terminals if they don't take c&s cards. Merchants who violate their solemn oath of office (just kidding) of course are another matter (professional development as we say in the ed business) or sanctions (as Obama says when he draws a red line) but I would say whether it is required or not, well over 95% of pos terminals do not out of hand reject a c&s card. It goes through with the transaction and not until the merchant sees the message signature required does the merchant know it's a c&s card and not c&p. And by that time, the transaction has been properly authorized and is on the customer's list of authorized but not posted transactions. It is then the merchant, who if he wishes to cheat, that then voids the transaction. Luckily while there have been a few reports of this, it hasn't yet spread all that much. Hopefully as part of the US changeover, if they go in the direction of c&s with c&p capabilities, mc and visa will put something together making it clear c&s cards are to be honored. How effective that might or might not be is the question for which at present we have no answer.