Most of this site can be viewed just fine without requiring you to login. But certain sections, such as the Vocabularium and the upcoming online game Capture the Dog, require you to login.
Rather than needing multiple logins or having to duplicate profile information, your metalogin logs you in to every sitelet of the Metapage.
First, you need a metalogin to use what I think are the most fun parts of the site -- the Vocabularium and the upcoming game Capture the Dog!
Second, there are (or will be) countless other things you can do on the Metapage once you are logged in. Your experience here on the Metapage can be purely informational or entertaining. If that's all you're looking for, don't create a metalogin. But many places on the site are interactive in some way. As the metalogin is integrated more fully into the metapage, you'll be able to contribute more and more. Submit your motto! Write captions for pictures! Edit your own page in the Friend Finder!