The thing I don't entirely get about tipping at Starbucks - I give my order to the person at the till, pay. It is only after I leave the till that they start prepping my drink, and I know whether it is made correctly or not (given their 'anyway you want it' ethos, you'd think they would be able to get it right all the time, I am batting about .500 - extra hot / ratio of syrup pumps and no whip seems to flummox some of them nearly all the time) and I am not going to tip someone when they will potentially screw up my order.