Yahoo! Mash
Description
Yahoo! Mash is a new social network launched by Yahoo! sometime early September 2007 to compete with MySpace, Orkut and Facebook in offering mashups of existing web services on a single user interface. The service is currently in beta on an invite only basis.
Mash has the unusual feature of letting a user edit other peoples pages, unless the user turns this feature off.
The social network is widely considered to have been created after talks for merge acquisition with Facebook fell through.