Facebook Groups

[faraway]

..... Facebook mined my Outlook contact list and cross referenced that to their database. That was enough for me to steer clear ever since.

That is a known extreme nasty behavior of FB. But you must have misinterpreted one of the many questions during the registration. You are asked for permission to access your address books. It is hidden behind a sweet question about your friends. FB uses that address to contact them and ask them to join FB too if they are no FB member or ask them to become your friend if they are already FB members.
I watched my wife closely when she created her fake FB account to make sure she does not grant read access to her address book.