There’s no need to register (very nice) just to toy around with it either. If you want to stop others from screwing around in your pages you might want to claim your site though, for which you’ll need to use your email address. But as long as you don’t link to it, all you need to do is save the URL that is automatically created for you and you’ll have your new site always at hand.
The layout possibilities are minimal, but it makes the sites look slick. No hideous MySpace effects thank you very much. It also allows for an open structure, meaning you can allow visitors of the site to make edits, and thus creating a true wiki of your own.