I have a strong feeling that at some point Reddit is going to have internal struggles with this ala Tumblr. Their consistent amendments to what you can or can post, as well as culture policing in various subreddits is bound to create additional controversies.
www.runads.com is doing the same for their mobile advertising campaigns.
The ad-tech industry is targeting mobile advertising as the Next Big Thing, and they're right to do so. Anyone not tracking and optimizing ads toward the permacookie will be left behind.