Either some third party could discover fantastic new search technology and steal the market, or internet search is solved and brand name is all that matters, so the company with the best PR will win. Either way, it shows that Google has lost its previously unassailable technological advantage.
I agree that a brand name advantage seems easier to tackle then a technological one. Especially when switching costs are so low. But then this is a pattern followed by many technological products. A technological advantage, followed by a few years lead followed by equivalence where their product demands a premium, outsell competition, etc.
Take Sony (portable radios, portable cassette players) or Canon (bubble jet). Innovation that was quickly equalised followed by a long period of leadership. You could even argue that a long period of technological superiority (say because of patents, trade secrets or even faster innovation) might result in an unbalanced company that cannot survive once superiority is lost.
Seems like a weakness to me.
Remember Microsoft at one time was one of the most respected brands around.
To me, that signals serious weakness.