Many YouTube videos are taken down for alleged copyright violations. But some of them are leaving digital tracks in cyberspace, thanks to a group of students at the Massachusetts Institute of Technology.

YouTomb (http://youtomb.mit.edu) is a kind of online burial ground for disputed YouTube content.

The videos themselves aren't viewable, but the information about them is pretty detailed. YouTomb posts stills and links to long-gone videos. The site includes why they were removed -- usually because of copyright issues. It names the person or company that requested the video be removed, along with the number of views it had and the number of days it was posted.

In some cases, the offending videos end up having a pretty good run -- some for more than two years, while others survive only a few days.

A November 2008 segment on "The Late Show With David Letterman" about Sarah Palin's infamous turkey pardon was taken down following a CBS request, although it had more than 88,000 views in the 204 days it was online.

Many of the requests come from large entertainment conglomerates such as Warner Brothers Entertainment Inc., Sony Music Entertainment, HBO, The Walt Disney Co., CBS, the NFL and others.

YouTomb is a project launched by MIT Free Culture, a watchdog organization devoted to open access to culture. One of the site's goals is to track the accuracy of the automated filtering technology YouTube uses to detect copyright violations. They also monitor what kinds of videos are taken down and offer advice to people who feel that a video they posted was taken down unfairly.