Here is an interesting post on the LJ Tech Blog about blocking social networking sites like MySpace from libraries. The proposal defines a social networking site as any site that allows a person to create a profile and contact others.
The term ‘commercial social networking website’ means a commercially operated Internet website that—
(i) allows users to create web pages or profiles that provide information about themselves and are available to other users; and (ii) offers a mechanism for communication with other users, such as a forum, chat room, email, or instant messenger.
You can read the whole text here.....