Auto checked?

I want to have the checkbox automatically checked by default. After showing a demo site to a client that used terms, the client showed me facebook which has removed the checkbox, it now has a messaging saying "by singing up you agree to the terms". They would like to remove the extra click, but still want it to show in the registration form. I may accomplish this using a form alter module, or adding a very simple piece of java-script, but it would be a cool feature to give the option of having it auto checked, I may end up doing that for the major of sites considering it's used by facebook and a few others.