I think everyone here understands that these are all layers of data-mining, and all the big players are doing it.

But it's the subtlety. Google (at least Google of old, who knows in the future) sort of offers you help as you're looking for things, just like in the example below about hotels in Istanbul. The average person probably doesn't understand what's going on under the hood there. People don't really know what Google knows about them. Facebook, on the other hand, is openly saying "We have all of this private information on you, and we're going to sell it to the highest bidder." It's the same, but different. One is PR friendly, the other is a PR nightmare.

This can't be a long term strategy for Facebook. People don't want to know that their information is being sold. They will tire of this.