Farmville had a massive install base. So they weren’t accessing that much data relative to the number of people that had directly authorized their app. The difference between it and the Obama app was the leverage that was allowed: less than 1 million people gave them access to their data, and they were able to use that to get deep profile data on nearly every US Facebook user - ~200 million accounts. Their attempts to do this set off all kinds of alarms, but Facebook went in and manually shut those alarms off and opened the floodgates to the data. Our data.

Considering that at least half of them - ~100 million people - would have consciously objected to helping Obama do anything, much less get elected, that should have been earth shatteringly scandalous and probably should have buried Facebook right then and there. But instead, the press celebrated this technique, right up until it helped create a result other than the one it wanted.