I don't think his statement helped his talk at all. It would be best to be explicit about it: "I don't think explaining a list of lessons learned is useful for you, so I've put together a few short slides to talk about my experience without presuming to prescribe an action for you"

There is nothing in that statement that implies the speaker doesn't care about the audience.

It's not a matter of what '..would be best..' - that's impossible to judge w/o all the context, and even then it's subjective.

My point is that there are some occasions where is does make sense to 'tell your audience you haven't prepared', so I disagree with your hard-and-fast assertion that 'you shouldn't tell your audience you haven't prepared', and the blogger's assertion that 'when you say “I’m not really prepared” in front of an audience you’re showing them the ultimate disrespect'. Such black and white rules don't seem valuable to me.

It's horses for courses..

Umm... Your sample quote, is, in fact, almost exactly what he communicated during his talk. Am I missing something?

Yes, he started out saying he didn't prepare. That's the whole point of the original post and this thread.

Right, but I thought you said "it would be better if he had simply said...", when he did, in fact, say just that. Never mind; I think we're actually in violent agreement.

I see what you are saying. The comment you responded to essentially said "it would be great if PB did X" when in fact PB did do X and they were not listening. That was actually one of my favorite talks of startup school but not really because of the format. The "unprepared" format won't work for most people.