I am not referring to any incident in particular. Bit it is difficult to protect people from scams partly due to their own greed. For example, you sometimes see scammers using the ancient three-card to fleece money from people in London.
The gold ring scam in Paris: https://europeforvisitors.com/paris/articles/paris-gold-ring-scam.htm
I remember somebody claiming to be selling "gold" chains real cheap on a London pavement because they were "stolen".
Some scammers also play on people's sympathy to part with money. (Please feel sorry for my young child, or elderly and ill relative etc)
Education can help people avoid losing big money in scams to an extent. But greed can convince some people to believe in the most ridiculous stories (or so the scammers would hope). An infamous seller once claimed that her special banknotes arrived by "airmail". She woke up one morning and find them attached to a balloon trapped in a tree and they are worth thousands. People who believe a story like that can't be saved.