Facebook faces probe for mining users' e-mail list

Click HERE
This may explain why u r getting spammed by a lot of unsolicited ads...ur email address was 'harvested' from ur friend's contact list when he signed up for a Facebook account. Some organization may even SELL these email contact lists to other commercial entities....

Facebook's unauthorised collection of more than 1.5 million users' e-mail address books.... Facebook harvested the e-mail contact lists of a portion of new users who signed up for the network after 2016....Those lists were then used to improve Facebook's ad-targeting algorithms and other friend connections across the network.

Relate to the 2014 compre AQ on how the internet exploits our tastes and dictates what we like and buy....
Consider also the 2017 compre AQ about how if the product/service is free, then we the users are the 'product' unknowingly, as we are being monetised by the company whose product/service we consume free of charge. As the adage goes, "There's no such thing as a free lunch."