“I recently read an article regarding the security of so-called “scrubbed” data. Netflix or some other company wanted to employ a third party to analyze some of their customers’ patterns of purchase — but as a precaution they removed (scrubbed) the customers’ names off the data. So theoretically, the people being analyzed were now abstract entities. However, out of curiosity they hired another company, to see if any of those unidentified customers could possibly be re-identified. It turned out they could. Not due to a fault of the scrubbing, or some security or software malfunction, but because other data and patterns of customer and citizen behavior were available online, and correlating these with the patterns of the anonymous customers led to conclude, beyond a reasonable doubt, the re-identification of many.”
http://journal.davidbyrne.com/2009/10/102409-internet-antichrist.html