I just love them.  They're so useful when you stumble across a source of data that you'd be too worried about emailing.  Plus - targeting by phone number! Fecking yay.

oh, thx for the tip...

agreed, but has prompted me to review the wording on clients email sign-ups!

although kind of hard for anyone to prove unless you could contact FB and ask why you saw an ad...

Business to Business. 

Scrape emails and phone off Yell etc for businesses to target.