Service.

In terms of User Experience Design, the web can learn a lot from the restaurant world —

For me, service is how people look at you, talk to you, engage you as human beings. It’s not about how fast they pick up the crumbs on your table or even fill up your water glass.

Christian Puglisi (Relæ) in Cutting it Down to the Bone, Eater

Later, he talks about giving the right amount of information to diners, ensuring that each person’s need is appropriately met —

I don’t like the idea of waiters pulling off monologues, especially when the people might not understand or want to hear it. So, better to spend time with the person who really wants to know about the weird wine they are being served or something like that.

These seem like really obvious things — do what you should do, not what you can do; treat users like humans; give them the right amount of information for what they want — but they’re often the first failure points in any user experience.