Facebook has had no shortage of privacy debacles lately, and it's taking steps to prevent another one before it starts. The company has instituted requirements for its Custom Audience advertising that, as of July 2nd, will tell them to ask permission for targeting ads based on contact info like email addresses and phone numbers. They'll also have declare how they got that contact info (direct consent, partners or a mix of both).
You'll have more control as a user. The "why am I seeing this?" link with each ad will show just who was responsible for the targeting information an whether or not your contact info was involved (say, an email subscription). If you object to a company using those methods, you can block their ads.
The system isn't perfect, as it requires advertisers to tell the truth about where they got their info. It's entirely possible that a company will simply lie about the origins in order to hawk their wares to customers. This at least creates a record of that deception, though, and may open the eyes of companies that didn't realize they should get your explicit say-so.