In Internet parlance, 2009 was WIN for Biz Stone and Evan Williams. Twitter the social-networking service the pair developed in 2006 as a way of bringing top-of-mind blogging to the text-message set was the killer service of the year, with some 18 million people signed up to broadcast their thoughts in 140-character bursts. Celebrities bought in too the world can now follow the daily thoughts and tribulations of everyone from Oprah to Shaq to Neil Patrick Harris. But Twitter came into its own over the summer as the best and sometimes only source of information from Iran, after authorities shut down media channels and Internet access in an attempt to draw a curtain over the violence that followed the presidential election in June. As more and more users logged on, Twitter accomplished what even Web behemoth Google could not: giving a real-time look into what people around the world were talking about at any given moment. The big challenge ahead for @biz and @ev? Figuring out how to monetize Twitter and its massive user base while keeping their ever beleaguered servers from crashing from the volume of new tweets.