One of the niftiest examples of an abstract concept in practice is on Seth Godin's Web site. Go to Permission.com and if you submit your email address, the first four chapters of Permission Marketing will be emailed to you, free. This touches on some interesting privacy issues that I've been reading about recently. Consumers will usually give up some personal data in exchange for a meaningful benefit. In this case, you have to decide if four chapters of Permission Marketing are worth your email address. In addition, you are prevented from entering dummy information because the chapters are sent to the email you provide. Enter a dummy and no one benefits, enter your real email and you receive a portion of the book and Seth Godin gets a confirmed email address. Now the ball is in Seth's court. He pinky swears on Permission.com that he won't sell your email address, but how can you tell if he's trustworthy? You really can't yet, but if he were to distribute that address, and you found out, his credibility would be degraded and you would think twice about offering him information in the future. So even though he would profit in the short-term, it's in his best interests to keep his word.