This could be what we consider "cloaking" in the ad industry. Ads containing legitimate content are submitted, but when a user clicks it, a risk assessment is d

This could be what we consider "cloaking" in the ad industry. Ads containing legitimate content are submitted, but when a user clicks it, a risk assessment is done based on the users information (ip/location/js enabled/saving cookies etc). If it's determined that you're unlikely to be a crawler or a person affiliated with the host site (google employee in this case) you're served a "Blackhat" ad, which is generally worded much more aggressively and against the TOS. High risk users are redirected to "Whitehat" pages which follow the TOS and generally don't attempt to actually convert a user. These high risk users are considered dead clicks. A few years ago this was an insanely profitable industry on Google Adsense, but they've cracked down a lot. The new major space for this type of advertising? Facebook.