I was reading somewhere that google cache was declared legal by some court, somewhere ;-)
Is it possible that google is ignoring a potential revenue opportunity in google cache. Only google can tell the actuall statistics but I think a fairly large number of people use google cache because its often faster than the original sites.
Google can start a program similar to adwords where these sites allow google to put advertisements on the page where there cached copy is displayed and they can share the revenues (in this case only google will have revenue reconcillation capabilities). Does Google even have to share the revenue? They can show the ads anyway.
Just wondering !!