This seems to be just from this app. That's based on the number of people who took the survey, and then an average of the number of friends that people had on Facebook at the time. That multiple gets you to around a million. Of course, there may have been other datasets and sources that were part of the data-gathering exercise as well, and then the targeting exercise that derived from that data.
When Brittany Kaiser gave evidence to us, she said that a good-sized working set of data, if you were going to plan a Facebook campaign, is around 40,000. If you have around 40,000 profiles with good mapping data, understanding who these people are, what motivates them, that's your good working set. Of course, then you can acquire look-alike audiences from Facebook as well, to grow that to help you target a much wider group.
Even if that were the limit of the data they acquired through Dr. Kogan's app, the power of that data is potentially significant.
Kogan also said to us that he didn't think that data, in and of itself, was worth very much, just with the surveying he was doing and the Facebook accounts they were linked to. But, of course, it was never intended to be used in isolation. It was intended to be used as part of a much richer set of data, of which this was going to be an important part.