Why we lie. Cheating, by just a little, is normal. And more corrosive to society than more serious crimes.
When you rate movies on Netflix, they produce recommendations of other movies you might enjoy. Same with Match.com profiles or Amazon purchases. They do this by using a process known as singular value decomposition. You math geeks might enjoy this. For some reason I found it fascinating even though I have absolutely no clue about the algebra involved in this.