this would be a breach of trust and short term would work great but long term is too detrimental.
same thing could've been said for search results, so at least that part is still "safe".
I'd be surprised if product placement isn't already basically at play. Charging companies for including/prioritizing their documentation in the training data, for example. Thankfully LLMs are terrible at the subtlety it would require for a direct marketing campaign.
Long term all of the major LLM platforms will have invisible ads, influences, and propaganda woven into the content. The temptation will be irresistible for these companies.