I discredit the PR stunt idea because I don't think SIAI would've dumb enough to pull something like this as a stunt. If we were being modeled as ones who'd simply go along with a lie- well, there's no way we'd be modeled as such fools. If we were modeled as ones who would look at a lie carefully, a PR stunt wouldn't work anyways.
Well, it doesn't really matter what the people involved were thinking, the issue is whether all the associated drama eventually has a net positive or negative effect. It evidently drives some people away - but may increase engagement and interest among those who remain. I can see how it contributes to the site's mythology and mystique - even if to me it looks more like a car crash that I can't help looking at.
It may not be over yet - we may see more drama around the forbidden topic in the future - with the possibility of leaks, and further transgressions. After all, if this is really such a terrible risk, shouldn't other people be aware of it - so they can avoid thinking about it for themselves?
Some research says that lurkers make up over 90% of online groups. I suspect that Less Wrong has an even higher percentage of lurkers than other online communities.
Please post a comment in this thread saying "Hi." You can say more if you want, but just posting "Hi" is good for a guaranteed free point of karma.
Also see the introduction thread.