Were Newton alive today and seeking clues to the nature of gravity rather than focusing on a falling apple, he could study falling Facebook shares instead.

If anything, they fall faster than fruit.

The social network's stock price had dived by 40 per cent since its initial public offering (IPO) in May before sinking a further 7pc to a record low shortly after trading began in New York this week.

Kim Kardashian sustained enthusiasm for her marriage for longer than that.

This week those who had invested in Facebook before its IPO was released from a 91-day lock-in period - designed to prevent shares from flooding the market immediately after an IPO - became free to offload their stakes. Many decided to cut and run.

The irony is that only a week ago Facebook announced it was to allow gambling with real money on its network for the first time, forgetting that trading its shares was the biggest Facebook-linked gambling opportunity.

Facebook's stock market journey does, though, offer lessons for those who tend to consider themselves financially ill-educated: that expert investors such as Goldman Sachs and George Soros, who invested heavily in Facebook, are sometimes no shrewder than a child flipping a coin; that the people who calculate IPO prices may need new calculators; and that if you are among the millions who never got the chance to invest in Facebook when it was a start-up, it is OK to update your Facebook status to "Experiencing Schadenfreude". Herbert Grimes