You can do auto-login (thats it - login without a password) for all regular users. A regular user is not an wiki owner, not a member of Administrator or Webmaster groups.

Make sure the IP address of the machine from where you want to do auto-login is in the list of allowed IPs.

The format of the auto-login url is: 

http://account_name.metadot.net/__metadot__/login?user[email]=john@mycompany.com&autologin=1