This video contains language which is not safe for work.  It is the opening scene from Reservoir Dogs. 

https://www.youtube.com/watch?v=V4sbYy0WdGQ

Why Does America Have Tipping - Cowen - Note what he recommends you do at a place you will eat at only once. 

http://goo.gl/6nMKlg

What Happens When You  Abolish Tipping 

http://goo.gl/aMFp9g

The Reverse Tip

http://goo.gl/dXWKNp

Theory on Tipping?

http://goo.gl/zTZkbN

$20 bill trick - Risky Tipping 

http://goo.gl/ZGrtXO

Bonus content: If you really have time to burn, here is a Freakonomics podcast and more links.

http://goo.gl/26ugiu