The internet giant is typically looking for ratings surges that are clearly outliers (say, a sudden burst of five-star ratings) as well as reviews that are "profane, hateful, or off-topic." And of course, any attempt to incentivize ratings and reviews is a red flag.

This doesn't mean that Google has a sterling track record. In February, it yanked the majority of reviews for Greenheart's Game Dev Tycoon despite there being no evidence of manipulation. And with the kind of one-week volume Google reported, there's a real chance that other apps and reviews slipped through the cracks. Nonetheless, the data shows that the quality of app ratings and reviews could be much, much worse.