It's that time of year where our thoughts turn to... buying stuff we don't really need. In China, we've just had the annual Singles' Day online shopping bonanza. And the U.S. equivalent of Cyber Monday is coming up next week. 

So what? As someone who hates shopping, I couldn't care less about what this means, or what people choose to spend their money on. But somehow, when you ask someone the question "What's the best or worst purchase you've made?", you seem to elicit some of the best stories.