Well it's not only this, or protection from LLMs training on LLM output. LLMs training on human output is also problematic.
I was traveling to an obscure small town, doing some "research" with LLMs beforehand. Every and each one told me enthusiastically to go to "Foobar square" (name changed) for the "best street food in XYZ town", some added a lot of colorful details.
There was no Foobar square in XYZ town. There was no Foobar square anywhere in the world. There was a SINGLE old Reddit comment, with no upvotes, to a unpopular post in an unpopular subreddit, where someone clearly badly misspelled the name of the square, and said something like "for street food go to Foobar square". Nothing about "the best" even.
It's all a lie.
I think this was a common game on city/town subs. It happened here, there was a post asking for a good restaurant and someone just made up a name. It went viral and people started posting made-up menus for the place, reviews, and for a couple of months any time someone asked about a restaurant this fictional place would get mentioned.
It was all done as a joke to see if they could get Gemini or ChatGPT to start recommending it.