I got eight out of ten. I thought that the Pacific coastline was much shorter (but I was imagining it as basically a smooth curve, and terminating it at the Bering Strait and somewhere down near India -- is that how they measured it, I wonder?), and I thought blue whales were much less heavy. Now I have to go find out how something that weighs 190 tons manages to propel itself!

I was surprised by one particular aspect of the blog comments; the recurring theme of "I don't think it's valuable to make estimates like this, because if I ever gave a project estimate of 'two to twenty weeks' I would be laughed out of the room."

What do you mean, you would be laughed out? If you're 90% confident that it's two to twenty weeks, then you should feel OK about saying so -- that's better than confidently saying "five weeks" and watching it turn out to be twenty! At least it should be better. It's a shame if people feel compelled to whitewash guesses like that to save face.