Several times in the past two years, the Department of Defense and other government agencies have purged "sensitive information" from their web pages. The latest directive orders all information on "weapons of mass destruction" to be removed. While this eliminates one source of this stuff, it is also available in many other places on the web (that have grabbed the data for their own web site). Not only that, but many of the major search engines have a cache feature. The cache captures the content of the web page to one of the search engines computers, so that if the web page itself is unavailable for any reason, all the user need do is click the "cache" link and up comes the "unavailable" information. The web is not only vast, it also comes with many built in backups. Once you put something on the web, you can't really pull it back.