WordPress MU

I'm not sure if it's supposed to work like this or not, but when a user tries to login and comment on another users blog they get this message:

You do not have sufficient permissions to access this page.

Do all of my users need to be made subscribers to every blog or is there a simpler way to do it?

Thanks!

If they are commenting on a blog that has the option checked "allow comments from registered users only" then yeah, they have to be added as a subscriber (at least) to that specific blog.