Once upon a time on WPMU it was ridiculously easy to be added to a blog. There was no email activation step so some of my school’s blogs had needless, excessive membership, like a black hole – no one could escape. That annoyance aside, the frightening side effect was the dashboard switcher or profile page that would list all blogs of a user. I worried about server loads if hundreds of dashboards kept listing hundreds of users blogs via the “get_blogs_of_user” or “get_active_blog_for_user” functions. With limited server resources, excessive queries are evil.

I also began to use the “get_blogs_of_user” and “get_active_blog_for_user” functions in an adminbar that loads on every page(front and back), so queries were the target, big time.

In summary, primary reason: if I set “Limit users Per Blog” to zero, there were no invites, no spammers – one member per blog. No more worries about excessive queries on the profile/dashboard/adminbar.

Secondary reason:, if I set up WPMU for students/classes I could limit membership to small groups for student(server load) management. SiteAdmin could see such groups forming under the SiteAdmin–>Blogs page.

This plugin worked for 2.6, but WPMU 2.7 added a toggle of the “Add New Users” form using SiteAdmin–>Options(wpmu-options.php#addnewusers).

I haven’t bothered to revise the plugin to limit the member count, as that wasn’t my primary goal. The extra step with email activation in recent versions of WPMU slows down the add user process significantly. Until I notice server load issues related to the profile/dashboard/adminbar, or a notice a user with a ridiculous number of members or a user belonging to a ridiculous number of blogs, I probably won’t revise the plugin.