Facebook (or whatever) probably tracked his location to a pub which triggered a beer ad. Guinness advertise a lot, so it's not surprising that particular brand should show up.
This. Sorry not to take part in the buzz, but I don’t think google etc. listen to you through your phone. Not because they suddenly respect your privacy, but because vocal data is far too inaccurate and costly to collect and use. As said by others, social media platforms use other means to learn an awful lot about you. It‘s likely not a coincidence, but rather the result of accurate collection of data.
Example: take a pic of your dog in your house and store it in the cloud (the pic). EXIF data will tell e.g. google where you live, google already knows who lives where (there are reverse online phone books) so they have your real name no matter what rubbish you wrote when creating the account. They also know through real estate sites that you’re in a rather good neighborhood, they don’t even have to look at linkedin in order to know that you have a good income (though they won’t refrain from looking there too). Moreover, inhabitants of your uptown neighborhood can usually afford say a Porsche, proven by the fact that some of them regularly stare at said website. etc. etc. etc. the list of information found that way goes on, of course including all sorts of information about your kids, in which football team they play, who are their friends, which school they attend. All this from a pic of your dog. And all this research is legal as it’s publicly on display.
Now, for a congress you go to a city you’ve never been before, and out of boredom you start talking to the guy next to you at the hotel bar. He is a regular visitor of the pfm website, and is threfore, according to google, likely to love Porsches too. As a pastime you start talking about, I don’t know, nice cars like porsches, and of course you’re both using the same hotel wifi.
Next day you meet again and are both astonished about the Porsche ads you get since your conversation, even though you can’t remember ever having visited their site.