Am I missing something? Everything I know suggest that I would have had to visit a Facebook site sometime between my Gemini request and my receipt of an email from Facebook. Or possibly have visited a Facebook site before my Gemini request and not have directly entered a URL or used a bookmark in the interim. AFAIK, those things didn't happen.
Those icons on your screen for Twitter(X), Meta(Facebook),
LinkedIn(Microsoft), ... are beacons. By "agreeing" to
display them on your browser you donate your browsing history
to each of them. They then sell your browsing history to
advertisers.
Easy peazy.
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