I've always thought it was because they provide content that is fungible. One porn video or picture is pretty much replaceable with any other, perhaps within a certain genre.<p>Compare that with Hollywood video, TV or the music industry. Is one movie or show really replaceable with any other or do you want a specific film, show or album.<p>So, by comparison they are a more competitive, freer market hence greater innovation.<p>The other fast mover is scripture, which is public domain and so finds its way onto each new medium very early on for similar reasons.