Please do not require to login!
The sharing via a second unique url would be great for teams and I could use it right away. If I have to convince all my colleges to login that would kill it for me :/
I understand the frustration of too many logins :)
If I do end up adding user accounts, it would only be to add extra functionality (persistent URLs etc) - the existing functionality + potential perma-link feature would all remain available without an account.
