[icebraining]

I think conflating a publicly accessible website with a private conversation - even if in a public setting - is specious. That said, I concede the point that some websites are meant to belong to the deep web, and while I wouldn't feel guilty about archiving it for personal use anyway, I wouldn't blame the author for banning archivers.

I'd say my general rule is closer to: if you allow search engines, you should allow IA.

W.r.t. your last question, historically the solution to that problem was simple and elegant: people used pen names to write what they didn't want to bind permanently to them. This way is also safer from unauthorized archiving - not everyone is as respectful of the author's wishes as IA.