Saw this at work... I work for a credit card processing company. The card companies have gotten together and made some new rules about tipping.
“Based on the card brand rules the tip tolerance must not exceed 20% and depends on the merchant category code. If the final transaction amount does exceed the set tolerance amount the merchant must obtain an additional authorization and process a separate transaction for the amount that exceeds the tolerance amount."
And merchants -hate- to run multiple transactions, because each one costs them money... a few cents, mainly, but they're as bad as soccer moms with coupon binders...
There was more to it, but a lot of technical jargony stuff, for different industries. Not sure how it'll work in the terminals, whether it'll automatically do a new transaction, or prompt for 'excessive tip' or something... some of them will currently require a password to put in a tip over 25%.