I reckon American Express must be one of the safest cos their charges are so dreadful than nobody accepts them
I had a problem with my Barclaycard when on a bike trip abroad. Apparently the card was being used to buy petrol at service stations so far apart so quickly that the same person couldn't have been using it. Whoops !!! too many "splash and dash" tank fulls.
Seems they fail to strike a balance, it's either too harsh or letting people get away with daft amounts on your card.