Even if it would be truly anonymized, once combined with th other vast amounts od data Google has means it is possible to tie the anonymized data to specific, or a plausible group of people.A bad anonymizing process would be a far more likely culprit, but by analyzing patterns, something AI and computers are good at, could yield interesting results.
It has already been studied and accomplished. Too many studies to name here, but for example, in 1997 a Massachusetts researcher succeeded at converting zip code, birth date, and gender info from voter-registration lists, into links to someone's medical records.
It certainly isn't anything new, it's been used for a long time to develop information; computers have just gotten more powerful so it can be done faster and by people and companies, not just government agencies who could through lots of people at the task. Pattern recognition with computers goes way back, Johns Hopkins University, for example, was doing research on it in the 70's.