From an IBM support eMail:
As the End of Service (EOS) of Lotus Enterprise Integrator, Notes, and Domino 6.5.x document outlines, April 30, 2010 is the End of Support date for Notes/Domino 6.5.x. This means the end of technical phone support and code fixes for all Notes, Domino, and LEI 6.5.x releases. You can also refer to the Lotus product lifecycle website for more information.
So here's the deal. If your running anything before say 7.0.3, you have to consider upgrades NOW. And dont just chuck em in - go and study redbooks, hire consultants (such as the rather excellent Bluewave, Turtle Partnership, Portal Partnership here in the UK and Eire).
Because running out of support software puts your business at risk. And may be breaching industry rules (such as FSA).