While quirky 404 pages like these are a nice change from the plain boring old 404 messages, I wonder if a lot of sites are losing visitors because of 404 pages

While quirky 404 pages like these are a nice change from the plain boring old 404 messages, I wonder if a lot of sites are losing visitors because of 404 pages like these. Has anybody got any stats about how many people see a 404 and never visit the site again? What I would like a 404 page to do would be something like this: Take the example of a content site, which has recently moved some pages around. If I land on the old URL which was linked in some other post, I would like to be transparently redirected to the new one rather than have a 404 thrown in my face. Similarly, if the link is a typo and no such page actually exists, it would be nice if the site tries to 'guess' where I want to go based on the URL and then provide a list of suggestions.