It's probably a little of everything
There's definitely been a shift over the past couple of years, in all forums, not just HD, where the new people have read that posting on forums help with their online presense. As such, they just post for the sake of posting.
I've certainly seen it in the graphic design forums too.
I'm a member of several Google specific forums and support centers, and the number of people that post the exact same post as the person 2 days previous, is pretty insane. We spend more time flagging and moderating posts than we do actually helping resolve issues