The FTSE 100 index of leading British companies has repeatedly hit new all-time highs this year. That is exciting – but it also puts me in mind of some of the investing wisdom of billionaire Warren Buffett. For example, Buffett famously said that people ought to be greedy when others are fearful and fearful when others are greedy. So there is clearly a fair bit of greed in today's market, could now be the time to be fearful? Some parts of the market, especially across the pond, have valuations that personally I reckon are hard to justify.