I was listening to a podcast the other day and one of the commercials I think was from Facebook (IIRC, it could have been Google...). It was directed toward students, so I'm pretty sure it was an organic ad, but there were several aspects to it that felt fairly personalized to me (bicycling and outdoor related) that I actually wondered if it was generated on the fly using an LLM.

FB knows me and what I like and they have enough of data on my searches that they could customize a pretty relevant audio ad that, now with LLMs, can feel really relevant and natural, especially with audio gen being so good.

My point though is I wasn't sure if it was LLM generated or not and that's stuck with me. Random ChatGPT copy-pasta is easy for me to pick out – most people do not write that well. But a sophisticated application of this tech probably approaches the it-could-go-either-way territory.