Surprisingly, overtipping can be pretty rational (well, at least according to Yishan Wong, who is quite a rational person, based on his posts on Quora)

http://www.quora.com/Life-Advice/What-life-lessons-are-counter-intuitive-or-go-against-common-sense-or-wisdom

Overtip everywhere you go. Usually, the only way to be treated like royalty at restaurants and service establishments is to be a celebrity (or royalty). The other way is to be the person known for tipping well. Especially at places you frequent often, make a point of tipping extremely well - at least in the 20 - 25% range or more (especially for small-dollar amounts, where you can tip high percentages without spending a large absolute amount). The idea is to stand out as the person who tips significantly better than all the other customers. The employees there will get to know you astoundingly quickly, they will memorize your preferences, they will learn your name (even if it is a weird ethnic one), they will ask after your health, and they will make a point of asking if there is anything extra that you'd like (and sometimes comp you stuff) and generally go to great, polite lengths to make sure you are happy. You will feel like a celebrity and when you bring your friends, it will impress them that the proprietor knows you and treats you so well. Real celebrities don't really come around that often (unless you're living in L.A.), so you will end up being the special customer they lavish all their attention on - the local high-roller. Especially if you aren't actually rich, you are just choosing to be a great tipper, it will make you seem like a really great person. All of this extraordinary service can be had by simply voluntarily marking up your own bill by 10% over the usual cost. Did you get a raise? If so, don't go eating at a nicer restaurant, stay at the same restaurant you've enjoyed all along, and just pay more for better service.