The Illinois Trial Practice Weblog has an item on Collaboration Between Law Firms Using Wikis:
Although there are many ways for lawyers to collaborate in a secure environment using the Internet, many of the “solutions” require the use of an outside vendor or other IT professional. At the BlawgThink 2005 conference in Chicago, I learned that some lawyers have had success collaborating between firms using wikis, a solution that’s both inexpensive and within the technical reach of many lawyers.
While wikis are easy to set up, and there are a number of hosted wiki providers that can make the job even easier, I’m not sure the security provided for stored data has been adequately tested. Also, I don’t believe most wiki implementations take advantage of SSL or other encryption to protect information during transit. So wikis may be a good solution for colloboration within a firm, or for public information, but personally I would hold off on building a solution using a publicly accessible wiki that would hold any confidential information.