This is one of the reasons why I'm generally not OK with "anonymized" data collection without an explanation of how it's being anonymized. It's almost always easy, often trivially easy, to correlate the data together and basically get a perfect recreation of whatever the original data was back.
Anonymization in the data reselling industry is often some form of md5(lower($email)). It's a joke. They even do that for extremely small search spaces like phone numbers. It's still provided at the individual user-level and even if the anonymization is done in a way that's irreversible, you only need to know a single event for a given person and you now have their entire history. For example, there's a popular email…
This x1000.
I have seen people invite others to eat lunch at restaurants that only accepted credit cards in order to elicit such a data sample.