I tip pretty generously. I think people should be more cognizant of the service industry workers who rarely receive gratuities for their labor. Specifically, hotel maids, who work incredibly hard and witness the aftermath of the most disgusting human behavior imaginable.
Also, when the person who delivers your newspaper every morning at 5:00 AM, regardless of weather conditions, sends you a Christmas card in early December, its so you'll have their home address. Hook 'em up.