It's pretty simple. You bought a product. If it's a good product, you are smart because you chose it. If it sucks, you're the sucker who got duped. Therefor, there's an incentive to think that things you own are better than they really are. There's a real name for this, but I can't remember what it's called.<p>Take a look at Craigslist whenever you'd like some more examples.