Because there is no such thing as anonymity on the internet, especially if you're able to buy browsing history. AOL released a slew of anonymous search results

Because there is no such thing as anonymity on the internet, especially if you're able to buy browsing history. AOL released a slew of anonymous search results in the early 2000s as a dataset. It took a few weeks (months maybe?) to start to determine who these people were based on patterns found in the data.[1] Even with aggregate or partially anonymized data you're going to be able to identify individuals based on habits and patterns. 1: https://en.wikipedia.org/wiki/AOL_search_data_leak https://en.wikipedia.org/wiki/AOL_search_data_leak