Grigory Begelman, Philipp Keller, Frank Smadja; Technion Israel Institute of Technology, Citrin Informatik GmbH and RawSugar at Collaborative Tagging Workshop WWW 2006
A site where you can have a secure, optionally private, ad-free wiki of your very own for a few dollars a month, or an insecure, ad-infested, public wiki for free. Neat-O.