I hate it when you order a coffee and the waitress comes by to ask you if you'd like a refill- naturally you say yes, because the cups are usually kind of small and one cup is never quite enough- only to find out when the bill arrives that for each refill or top up of your crappy diner coffee you've actually been charged an additional 2.50$!
I could understand if I was getting an espresso based drink, but plain drip coffee? Please...
If you're going to charge people at least let them know. My boyfriend and were charged 10$ for coffee between the two of us. That was more than my breakfast!