John Plender in the FT hedges his bets like a master in this long think-piece and finally concludes that, yes, maybe there is, and maybe derivatives will be where it starts. Michael Lewis at Bloomberg, mildly furious at the sort of people who "travel joylessly to the base of a Swiss ski slope and worry... not privately, with dignity, but publicly, to anyone who will listen" says it's all no more than attention-seeking.
They're both worth reading if you want to start your own train of thought. Food for thought, too, from the FSA with its new Financial Risks Outlook. Personally, I'd like to see a little more attention paid not to shocks like the ever-imminent bird flu pandemic, but to the sort of widespread delusional behaviour that starts quite a few crashes on their way - think of the dot-com crash and ask "Are investors fooling themselves like that now? If so, would we know?"