"In the previous Coffee Break Training on the Invisible Web we discussed how a lot of valuable content is not available through a typical Web search engine. One of the reasons for this is that search engine spiders aren't able to log into a password protected resource. LLIS [Lessons Learned Information Sharing] is a good example of a Web resource containing original content that is password protected. LLIS is an online resource that allows some 40,000 emergency responders to share and find information critical to their work. LLIS original content is 'invisible' to search engines."
Coffee Break Training - Info Search and Web 2.0 Series No. IS-2009-7
United States Fire Administration: http://www.usfa.fema.gov/