[makomk]

I think a better analogy might be "If I take a few hundred thousand MP3s and come up with a clever way to reduce each to a short representation of its genre, mood, tempo, etc that can be used to identify similar music, then throw away all the original MP3s, am I still in possession of the original music". The whole point is to turn the individual data into broad, general categorisations that are easier to handle because they contain much less information. Remember, they're using this for ad targeting, and the reason they're doing it is so they can target broad groups of people rather than having to manually go through and target ads at each individual one by one.