Yeah, so maybe after a decade and trillion dollars or three of selling recommendations with impunity they'll get slapped with a fine that's 1/1000th of that.
It's an interesting point, and it comes down to 2 questions: (A) what is considered "product placement," and (B) who regulates it (at least in the US, where I am)?.
tl;dr - If the placement you're imagining is anything beyond "merely showing products or brands in third-party entertainment content,"[1] the FTC would not consider that to be "product placement," and it would be subject to their normal online advertising policies.
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Let's start with question B: who regulates it? In the US, the 2 relevant regulatory agencies are the FCC and the FTC. The FCC regulates disclosure of sponsorships[0] in traditional broadcast (TV and radio). That's why TV broadcasters need to include "promotional consideration provided by"-type messages in the credits - the FCC's rule is basically "the viewer should be told who is paying for this."
The FTC, which regulates online advertisements, does not require disclosure for product placement. However, they have a very narrow definition of the term, which it describes as "merely showing products or brands in third-party entertainment content" [1] (there's our definition for question A).
Not outright illegal, but in some places it's often required that what you're seeing is clearly an advert, or contains advertising.
For example, a watermark or logo is shown at the start of a broadcast containing product placement in the UK. Prior to 2011, it was 'forbidden' for broadcasters entirely.
(Quotes because you could still broadcast films that may arguably have it)
The UK.
It was outright banned for the longest time. I see now according to wikipedia they allowed it in very limited contexts in 2011, but almost all scenes with product placement are still edited out of most media, leading to shorter runtimes on most movies.