This was the original intention of the pioneers of the WorldWideWeb as an open collaboration medium.
From WikiPrinciples
See Also
http://usemod.com/cgi-bin/mb.pl?SoftSecurity-- RicardoStuven
Question: Are you allowed to freely copy information from wiki sites, and don't wiki sites ever run into legal issues?
Answer: No, you are not allowed to freely copy information from Wiki sites. Under copyright law, you are not allowed to freely copy anything from anywhere unless the work is accompanied with an explicit written notice that either states it is in the public domain, or that copying is explicitly permitted within the terms of the copyright. On works without a copyright notice, the copyright implicitly belongs to the author, so you may not copy it. That means you may not copy text, images, sounds, or anything, unless you are given permission to do so. However, under the terms of what is called "fair use," you may quote limited portions of a work for the purposes of commentary, criticism, or reporting. Of course, this doesn't even touch on the fact that copying work and passing it off as your own -- a.k.a. plagiarism -- is the foulest form of theft, and should be punishable by prolonged torture of the most medieval and disfiguring sort.
See also: WikiCopyRights, CopyrightInfringementInWiki