Facebook has used Like buttons to record information about users, websites and times in order to show what they describe as more interesting and useful ads since last year.
Yesterday Facebook announced they are continuing to roll out online interest-based advertising and will now begin including information from pages that use Facebook's Like button and similar social features.
You can opt-out of interest-based advertising by using the Digital Advertising Alliance AdChoices program, which provides a mechanism that allows you to opt out across more than 100 companies. Additional tools are provided in the advertising controls on iOS and Android devices.
You can also turn off this kind of advertising from the ad settings page right on Facebook.