This is a bit of a tangent, but at some point I find the "it was really an acquisition" thing becomes rather silly, as there is very little difference between hiring people specifically because of their experience and ideas in a product area and a startup of some people with experience and ideas but no actual product yet. Maps and Android definitely fall under that second group, as Where 2 essentially thought that web mapping was a good idea, but hadn't actually done it yet, and Android didn't release
anything until two years after acquisition, let alone ship an actual phone (which came a year after that).
There can be insight there (one great property of startups en masse is that they serve as a great experimental method for proving zanier ideas will work or market segments can exist if a product is made for them), but there does come a point where it's like saying Google's success in AI research is because they spotted AI researchers and snapped them up. Well...yeah, employees usually are hired for the job they were hired for.
Regardless, the original poster's criteria was "Google continues to validate its service not by competing on quality or feature distinction, but by throwing gobs of cash at it", which I think the GP's examples clearly contradict, as all of them have continued to gain quality (for some people's definition of quality) and feature distinctiveness.