There is a pretty big assumption in this article. The assumption is that Things will change, and google isn't smart enough to change their business model to compensate for changes. If ad revenue goes down to the point that google can not support their services, they can supplement that with a small charge for all of the services they offer. I'd happily pay a couple bucks a month for the google maps, reader, email, voice, translation, calendar, docs, wave, etc. They have many option available to them that may not be obvious now, but may be an option when the "Ad Bubble" pops.
Plus it sounds like they are breaking into other areas, ie ISP, etc.
I think they've shown enough intelligence to not cling desperatly to a failing business model, assuming things change enough to make their business model fail.