The facts that Facebook saves and keeps all interaction and user generated data and their engineers can access that data should be nothing new to you: Google, Amazon and every sane internet company do it too because they want to make decisions based on data.
The author clearly doesn't understand what he is talking about and doesn't try too hard to understand it; he wants to be sensational instead. Oh well.
They don't need the raw data to make decision. Statistics are enough (and even better, most of the time).
Keeping information that almost anyone would think of as private (search history for Google, list of purchased goods for Amazon) is insane. Literally. This kind of data can sort people by political opinion and sexual preferences, for one thing. This kind of data has already been used to spot or incriminate dissent. At the scale of these companies, this can go very wrong.
How they are using this data right now isn't relevant. The fact that every big internet company is doing it doesn't make it acceptable. The fact that no one bother doesn't make it normal.
You need the raw data in order to be able to calculate statistics in the future about relations you don't anticipate now. Also keeping only aggregated numbers would mean you give up on data mining.
I don't know if this use of data is "insane", but companies doing it get a clear competitive advantage over the rest. If governments decide to restrict it with some kind of regulation, there would be a clear cost in a less efficient economy. People are willing to give up privacy in order to gain convenience, otherwise they wouldn't be using these services. All these factors say we are going to see more data gathering in the future.
The author clearly doesn't understand what he is talking about and doesn't try too hard to understand it; he wants to be sensational instead. Oh well.