Ads in an LLM, such as nudging users to pick a certain solution or brand, could easily be orders of magnitude more effective than traditional banner ads. Certainly such numbers are possible if you design the product to fit. We have hardly even seen the beginning of that yet.
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I can't think of a greater incentive to only use open weight models than ads.
Disclaimer: I already use open weight models only since ~Jan this year and very happy about it.