You can rename the field to say whatever you like under Manage Form Fields--the Facebook could say "Facebook Business Page", and that would show up for the user.
Right now, that's what it does--you put a Facebook URL in the field, and when the listing is displayed, there is a "Like" button in the listing itself.
The Twitter button works similarly, except that the end result in the display is the Twitter "Follow" button.
Linked in shows a button for LinkedIn Profiles. It only works with actual business listings, not personal ones (that's a LinkedIn issue, not a BD one...we tried to get around it, they don't allow it)