Word of mouth is famously the best kind of advertising there is.
Cab drivers are notoriously chatty.
Cab drivers are now chatting to their captive passengers about holidays and other treats they’ve enjoyed, courtesy of canny advertisers.
See here, if you want a cabby to do your selling for you.
P.S. I chat to a lot of people too, so if anyone wants to give me a free Caribbean holiday to talk about, then please contact me at email@example.com!