The failure of Harrelson's AMA was in a mismatch of expectations between him/his PR people and the reddit community. Whereas the longstanding tradition on reddit is a back-and-forth dialogue between the users and the OP, with the users deciding which conversations gain prominence, Harrelson/his PR person approached it like a late-night talk show.
Honestly, as harshly as reddit came down on Harrelson for that, it was entirely avoidable with even the most basic preliminary research. It's hard to feel bad for Harrelson, and it's similarly difficult to imagine that savvy PR types would be put off by the response. It's pretty easy to see what leads to a successful AMA, and not particularly difficult to prime your client for it.
Honestly, as harshly as reddit came down on Harrelson for that, it was entirely avoidable with even the most basic preliminary research. It's hard to feel bad for Harrelson, and it's similarly difficult to imagine that savvy PR types would be put off by the response. It's pretty easy to see what leads to a successful AMA, and not particularly difficult to prime your client for it.