A couple of months ago the Austrian law student Max Schrems asked facebook to send him all their data stored about him. All Europeans have a right to do this. Because facebook is based in Dublin, Ireland. It took a while and then facebook sent Max a CD with 1222 PDF files.

Schrems was surprised how much the social network knows about him and his friends. And how much it remembers. In theory, people at facebook could read all of his facebook messages. And find out what he has written on criminal law.

The content of these messages might interest advertisers who place customised adverts. Customised advertising probably earnt facebook around two billion dollars in 2011. What Schrems writes to his friends might also one day interest the police - or hackers. facebook keeps the messages even after Max has deleted them, deep down in its servers.

And facebook knows exactly when Schrems writes messages. And it remembers when Schrems logs on. So even weeks later it can be established precisely at what time Max used facebook.

facebook also sent a CD with data to Schrems' friend Lisa. It knows much more about her because Lisa has taken photos with her i-phone. With GPS coordinates, the data can be used to work out exactly where she was.

With biometric facial recognition, which Mark has introduced to facebook, it is possible to know about millions of people exactly who was where when.

So it would be nice to know much more about Max Schrems' data - for example which biometric data facebook stores. But facebook says that they don't want to reveal any more. It's a confidential business matter.

Schrems has now complained to Ireland's data protection commissioner, who only recently has started an audit.

The graphs: 1.222 pages // logins // message activity // network // pictures in vienna // wordle