Facebook assures users that we should not be worried about privacy issues with targeted ads. They also remind us that advertising helps keep Facebook free:
Advertising helps keep Facebook free. We believe we can create value for the people who use our services every day by offering relevant ads that also incorporate industry-leading privacy protections. In our view, this is a win-win situation for marketers and for you.
via Relevant Ads That Protect Your Privacy | Facebook.
But remember, if you are not paying for it, you’re not the customer, you’re the product being sold!