Continuing the discussion from Group seems to have a limit of 201 members:
We have a forum for the backers of our Kickstarter campaign. We want certain categories to be read/write only to them, while other users (i.e. everyone) can only see them.
We are adding users to the group by an external script and currently we have a group of about 3,500 users. However, the group UI is now completely useless – there is no way how to check if user is part of the group or remove him/her from the group. I think it would be very useful to have a list of group a user is member of on the user’s page. One could then easily modify user’s membership there.