I have my users sign up before they can add any content, but I'm going to be implementing "lazy registration" soon, so that they can add their content, see how they like it, and then sign up if they'd like to. It's less of a barrier of entry and I think it will help drive more content being added.

See #1 here: http://www.smashingmagazine.com/2009/06/23/10-ui-design-patt...