Well, it's not unethical like you're injecting babies with a controversial drug. It's quite mildly unethical - a reservation is a promise. Promising something with a fake name is a little unethical - you're asking someone to do something for you, but offering no avenue of recourse if you don't hold up your end of the bargain. I think in this case that it's unethical to the same degree that taking some ballpoints home from work is stealing.