Is it possible to omit password from fast user switching and/or login screen?

I'd like to keep user passwords and require them when doing any administrative tasks as they are required in the default installation on Mac OS X.

Is it possible to be tweaked/hacked so that OS X won't ask for password when switching users? Or so that OS X won't ask for password in the login screen?

It is also essential that password is required for any remote login attempts — as they're in the default installation — be it SSH, SMB, VNC or the like.

I'm using OS X Snow Leopard 10.6.6

Case example (added after first answer):

I have two administrator accounts which I would like to allow log in and switch to locally without entering password. With "locally" I mean the login screen that is shown when computer is booted or user has logged out; and also the fast user switch password prompt, which is shown when the password-protected user is selected via fast user switch menulet.

Password should be entered if an administrative task is initiated. (I would rather not want a one common administrator account, but separate users and separate passwords.)

If user wants to login in, for example via SSH, the password should be entered. (I would rather not want separate "remote-access accounts", because I would like to use my accounts' resources hassle-free.)

Is it possible to be tweaked so that OS X won't ask for password when switching users? Or so that OS X won't ask for password in the login screen?

As long as they are not administrative users, yes. (Since you indicated you still want passwords for administrative tasks.)

It is also essential that password is required for any remote login attempts — as they're in the default installation — be it SSH, SMB, VNC or the like.

In that case, you must only allow logins for administrative users.