Three jam-packed days, and 52 startup demos later, we finally have a winner for this year's TechCrunch50. Every day, the presentations just seemed to get stronger and stronger. There were so many strong contenders this year that we are awarding five jury selection prizes, in addition to the top prize. But there must be a winner, and that winner is...Yammer. Yammer is Twitter with a business model. Created by an existing company, Geni, to scratch its own itch, Yammer takes the familiar Twitter messaging system and applies it to internal corporate communications. There is such a huge demand for this type of service that 10,000 people and 2,000 organizations signed up for the service the first day it launched on Monday. Anyone with a corporate email can sign up and follow other people in their company. But if a company ants to claim its users, and gain administrative control over them, they will have to pay. It’s a brilliant business model.