If you've ever made use of the eXcentrics World custom controls collection (eWorldUI) then you really should head over to the Web site at http://www.eworldui.net/ and sign the petition. I won't bore you all with the details as all of the information is on the Web site.
If you haven't made use of the controls before, where have you been? Matt has created some great controls over the last couple of years for ASP.NET, many of which I have used in various projects. Even though you haven't used them before, head over to the site and sign the petition anyhow, at least that way if they get reinstated you might have the chance to benefit!