First Things First...
Everything is optional. You don't have to give us any information. However, you may find the site slightly more useful if you supply your Last.fm user id, but it is by no means required.
If you change your mind later, come back here and click the "Forget" button. Your session will be cleared and it will be like you've never been to the site before.
To be perfectly honest, we're not doing anything with last.fm user names yet. But we plan to, and wouldn't it be nice if things worked out of the box for you when we turn the features on?
Ready, Set, Go