The study, which will be presented at the ACM Internet Measurement Conference (IMC) in November, looks at the targeting behavior of Google and Facebook. While the goal of the study was to understand targeting in general, the researchers discovered that gay Facebook users can unknowingly reveal to advertisers that they are gay simply by clicking on an ad targeted to gay men. The ads appear innocuous in that they make no mention of targeting gay users (for instance, an ad for a nursing degree). A user's sexual orientation can be leaked even if the user made his sexual orientation private using Facebook's privacy settings.
This study was done as part of a broader research project to design techniques for making advertising more private.