A 'super user' feature available only to web masters (or only to main administrator) would allow them to login as some other user.

Many times I get requests from users that have accounts on my site but are not web savy to post news or forum messages for them. It would be nice if I could login as them without having to ask their password.

Basically if you are a webmaster you would have access to a login like page, only username, no password, that allows you to login as someone else. The only way to go back being yourself would be to logout and login again. This is similar to the 'su' command in Unix.

Cheers,
Marius