How about this: allow me to play with the tool without logging in or creating an account. If I do create something, set a cookie and show me a big nagging message at the top of every page on the site from then on saying "you have unsaved work - you can view it here, but you should create an account to save it permanently".
I get a feeling if he did that, people here would say something along the lines of 'why are you nagging me to save my work - just let me play with your service and decide to create an account on my own.'
