"You should go do that right now, even if you're not a big Delicious user anymore. It takes 30 seconds to do and is something good to do for yourself and for the good of the Web. If you don't, that data will disappear. "
http://www.readwriteweb.com/archives/why_every_single_person_should_take_30_seconds_to.php
Why you shouldn't do it
"Serious Changes to Delicious Terms and Privacy: Link Censorship and Discretionary Deletion"
http://www.zdnet.com/blog/violetblue/why-you-should-think-twice-about-opting-in-to-the-delicious-avos-transfer/331