Does a webmaster have acess to know the facebook ids,& passwords of his clients/members to post on their walls?
I use opensiteexplorer.org with Linkdedective to filter the type of links. These 2 tools are very powerful if you like to find out your competition's back-links.
Normally you are not able to find the email ids of users like that. If you wish to have FB trafic it will be best to start the FB page or join a running one and try to obtrain traiffice by creating links there. hope you get what needs be done.
Not necessarily, password and ids are not required as a third party can post to Facebook walls via permissions being granted