There are way <i>way</i> too many of these sites and frankly even just having one breaks the web.  Look at this list of dead shorteners: <a href="http:&#x2F;&#x2F;archiveteam.org&#x2F;index.php?title=URLTeam#Dead_or_Broken" rel="nofollow">http:&#x2F;&#x2F;archiveteam.org&#x2F;index.php?title=URLTeam#Dead_or_Broke...</a>  Imagine how many hyperlinks each takes with them when it dies and how many pages reference those links.  Just stop it!