This is how the business of online promotion works. I had a first-in-its-niche company that was copied by spammers and seriously outcompeted with this kind of under-the-table promotion, which I had, to that point, refused to perform myself. And my company hurt substantially because of it (though it was ultimately destroyed by a legal threat from a Fortune 100); went from the only provider to third or fourth place, despite indisputable superiority to the spammy, pump-and-dump competitors.

The reality of online promotion is that if you want to win, you have to play the game. That means paying for placement in link rings and astroturfing hard. It means ignoring official advice from all platform providers as disinformation. Critical to the survival of any company is amassing a large multi-million dollar war chest before a lawsuit comes knocking, because the lawyers will be taking their pound of flesh, especially if you're going against a corporate bully that is more than happy to spend tens of millions of dollars just to teach you that they're not to be defied by the peons. Doesn't matter what the law actually says, only big companies can afford to fight.

This all being the case, I seriously doubt the FTC will make a real dent in undisclosed promotion, no matter how aggressive they get. Undisclosed promotion probably makes up 30% of the content on the web.

This case is likely as simple as FTC going after WB mostly because they knew they could get some good revenue out of them.