Viral Loop is a new book by Adam L. Penenberg. Many of the iconic companies of our time—eBay, Facebook, MySpace, PayPal, Flickr, Twitter—unleashed what is known as a "viral expansion loop." To use the product means having to share it. The end result is a company that spreads rapidly, scales quickly, and has the potential to create staggering wealth. "Penenberg discovers the perpetual motion machine for business and marketing... Buy this book. Catch a virus. Make a fortune." --Jeff Jarvis
