It's a small thing but when you buy a cup of coffee it's more or less a good with very small service component. Sure the coffee can taste good or taste bad but really it's a tangible product.
As soon as they ask you if you want sugar you need to make the choice "do I wish to enter a service relationship or not?"
Will they remember, will they put in the right amount, will they stir your coffee, will they use the correct type of sugar?
The poor girl who just forgot to put sugar in my coffee got all nervous as I took the photo you see. I wasn't cranky but I did just have an extra blog post to write.
Tangibles reliability assurance empathy and one other (I can't remember) are all the components of quality in a service product. That makes the production of a service product that much more tricky.
UPDATE: Chopper has his own service problems with Subway