I have set up a private blog in Blogger, and now I am adding users who will be able to see the blog under Settings -> Basic -> Permissions -> Blog Readers -> Add Readers. It seems that I am restricted to 50 users, and I need to add 70+ users. I am wondering if there is a limit to 50 users, and if so, if there is any workaround?
I believe that the limit is 100 invitations - ever. It doesn't matter if those invitations are accepted or not, once they're sent, they count towards the limit.
Could it be that you've added 50 invitations before now, and so the current 50 mean you have reached the limit? (Or maybe Blogger has changed the limit).
Also, once you have reached the limit, I don't believe that there's any way to extend this.