I used the share function to invite some colleagues to view and/or collaborate on a mindmap. The link is however going to a registration page rather than directly to the mindmap. This is a bit counter intuitive and I think it would be better to add 2 options when sharing that makes it work like Google Drive and Dropbox.
1) Make the mindmap public to anyone who got the link. Users see the mindmap but most register with the invited e-mail adress to edit it (default).
2) Require log in like it currently works.
My colleague flat out refused to sign up to the mindmap despite the mindmap being made to help explain some of her work. So forcing registrations before people know what they get is a very big obstacle.