I'm calling "Srawman" on this.
The correct conception is that it could be sold and the Market Economics Fairy has predicted that it will be sold as soon as a willing buyer and willing seller agree on a price. Indeed, if Facebook fails, all their data will almost certainly be sold along with the rest of their assets.
Likewise, Google has an increasingly strong incentive to sell user data as its perceived value increases and the cash flow per "unit" decreases. That Google sees this as a distinct probability is clear from their privacy policy which gives them the right to use user data "to develop new services." No one should be surprised by this because failing to reserve rights to a potential revenue stream would be irresponsible behavior by Google management.
If the thesis of the article is correct, sale of data is increasingly likely as the online advertising model pivots away from personalized advertising and the attractiveness of creating alternative revenue streams from the data increases.