On Facebook, there are two ways a person can report a potentially bad ad. One way is from within the ad itself. On every display ad on Facebook’s network, a person can click the “X” on the top right corner, which launches the following window:
From here, the use has the option to hide the specific ad, or all ads from the advertiser. Once a selection is made, a second window appears to allow you to choose why it should not be shown:
Based on that selection and feedback from other users, the ads policy team at Facebook will review the ad and – if appropriate – remove the ad from its site.
On a mobile device, the process is very similar: