More to the point, I'm not even sure that, in principle, it is possible to truly anonymize this data without spoiling the data science easter egg hunt. And the easter egg hunt is arguably the entire point of this kind of data collection.
You can do something like k-anonymizing the data and then destroying the original, personally identifiable data. But k-anonymity has its limits, too.
Every other strategy I know of assumes that it's OK to keep a private copy of the original data, which works well if we're talking about scenario such as a source that needs to keep the raw data (like a health care provider) providing the data with a semi-trustworthy external party such as a health researcher. But it doesn't address what I'm guessing is the main concern here, which is that, even if you accept for the sake of argument that Google currently has no intention to do gross things with the data, they can't make any promises that will hold indefinitely. It's a long-lived organization that whose policies might change with any change in leadership, market, or even political conditions, so any promises they might make are simply meaningless in the long run. As they would be with any organization, regardless of the presence or absence of any present-day warm fuzzy feelings.
