I can't post on HN without an account. How many people upload videos there? (Assuming that it is even possible for an average joe to upload porn there).
Just too small I think. It's neither hosted on a common forum software or worth targeting specifically. If you turn on `showdead` in your profile you can see the caught spam. It's usually pretty thin on the ground, and when it does it occur there's almost no diversity, suggesting just 1 bot source being interested in the site at a time.