This week's book giveaway is in the OCAJP 8 forum. We're giving away four copies of OCA Java SE 8 Programmer I Study Guide and have Edward Finegan & Robert Liguori on-line! See this thread for details.
Building Web Reputation Systems by Randy Farmer and Bryce Glass is a fascinating book on the topic. One important point is that reputations are not portable. Your reputation on one site means little on another. But on the other hand, each reputation does say something about who you are.