The missing manuals

Nature, they say, abhors a vacuum, and David Pogue has created a business selling "books that should have been in the box". That is, manuals for popular consumer software and hardware products.

"Missing Manuals ... are not only bestsellers, they're the most popular books on their topics."

So does this mean you should charge for the manuals you produce? If you don't ship good user documentation, are you passing a revenue opportunity over to someone else?

What do you think?