> by participating in AMAs, they enrich Reddit's community
That's the part I'm skeptical of, at least keeping in mind what community means in the HN sense. They don't really seem to be part of the Reddit community at all; they're more like the "content" that the Reddit community is discussing any given day. What's more interesting about the HN community to me is that some pretty accomplished people are actually part of the community.
Given the quality of questions/answers in a typical AMA, I'm not even sure how it's different from just linking to an offsite TechCrunch interview. Is it just some kind of fuzzy feeling of having participated?