The point is that it is actually fairly easy to trace information back to a user. People who are not familiar with this kind of data just don't realize how little you need to uniquely identify someone.
I am a little surprised to see that people who are generally uproar against companies not respecting privacy think it is perfectly ok to do it if it is for "science".
This is one of the big reasons why academics cannot release data BTW, especially in the social science: anonymizing data almost inherently means destroying valuable information.
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The point is that it is actually fairly easy to trace information back to a user. People who are not familiar with this kind of data just don't realize how little you need to uniquely identify someone.
I am a little surprised to see that people who are generally uproar against companies not respecting privacy think it is perfectly ok to do it if it is for "science".
This is one of the big reasons why academics cannot release data BTW, especially in the social science: anonymizing data almost inherently means destroying valuable information.