The Policy for Responsible Use of University Computers and Information Systems (Executive Memorandum No. 16) prohibits sharing passwords.
Included in the account claim email is the following text which is also published on the "protect your identity" web page http://its.unl.edu/protectyourself/
"Protect your passwords and do NOT share them with anyone. Sharing account information with people you know or through social engineering are the most common reasons for identity theft. The university will NEVER ask you for your passwords. If you fear an account may be compromised, change the password or contact the Help Center immediately. (Your university password can be reset at the password reset website https://trueyou.nebraska.edu/) ."
We also publish a page with recommendations on how to choose a strong password.