Stupidity in Published Scientific Literature

Pink News reports on a publication reporting that some adverts on Facebook are targetted at gay men exclusively even though they have nothing to do with sexual orientation. A quote from the published article [pdf] (emphasis mine):

Alarmingly, we found ads where the ad text was completely neutral to sexual-preference (e.g. for a nursing degree in a medical college in Florida) that was targeted exclusively to gay men. The danger with such ads, unlike the gay bar ad where the target demographic is blatantly obvious, is that the user reading the ad text would have no idea that by clicking it he would reveal to the advertiser both his sexual-preference and a unique identifier (cookie, IP ad- dress, or email address if he signs up on the advertiser’s site).

How does something get through peer-review stating that if someone signs up to a site with their email address they "would have no idea" that the people they are signing up to will have their email address?

One other point. The experiment run to find these conclusions involved three Facebook accounts, 2 of straight men and one of a gay man (with all other details the same). Surely that's far too small a sample for any meaningful conclusions to be drawn?

The paper is entitled "Challenges in Measuring Online Advertising Systems" published in  Proceedings of the 10th ACM SIGCOMM conference on Internet measurement conference