The thing is, though, before the Harrelson backlash began, there was nothing to signal to celebs, or anyone outside of Reddit for that matter, that there was a "right way" to do it. I'm still not convinced that there is.

Sticking with the Harrelson AMA for a moment, that thread got voted onto the front page even before Harrelson answered a single question. In fact, he had made it clear that it would be three or four hours before he came back and answered any questions at all. Which indicates that redditors up vote celebrity AMAs out of sheer excitement for having the celebrity drop in at all. So why shouldn't publicists and celebrities think that treating it like any other press event is "doin' it right"?

I don't think Harrelson's behavior explains what happened with that AMA. In fact, looking back over the top AMAs of all time, it looks to me like a lot of those were just as transparently about plugging the celebrity's recent work. Rather, it looks to me like the top-voted comment set a lot of expectations, and a lot of redditors staked their response to the entire AMA on how Harrelson and company answered that one question. When he blew it off, they turned on him.

Unfortunately for Woody's PR team, they greatly misunderstood the AMA concept, and suffered accordingly.

I think that's a misreading of the consequences. They got publicity out of that. The name of their movie was on the front page of Reddit for hours before the backlash began, and even the bad press they got afterward raised the profile of the movie a notch. If it's unfortunate for anyone, it's unfortunate for redditors who like celebrity AMAs, since celebrities can now see how quickly redditors might turn on them, and will be reluctant to stage AMAs in the future.