The denizens of Silicon Valley seem a bit like pre-Copernican astronomers: They assume the earth revolves around them. Look at all the discussion that’s gone on about whether the investments in “Web 2.0” companies represent a “new bubble.” If there is a Web 2.0 bubble, it’s about the size of the average bubble in a glass of Veuve Clicquot. Meanwhile, real bubbles – big gnarly ones – have been blowing up all over the place. There’s the real estate bubble, of course. And then there’s the copper bubble and the various other metals bubbles. And there’s the emerging market equity bubble as well as the emerging market debt bubble. It sometimes seems that everything’s a bubble these days – other than tech stocks, that is.

But about two weeks ago, things changed. Investors began to get nervous. Risky investments, they realized, actually entailed risk. Since then, investors have been moving out of risky investments and into safer ones, and some of the big bubbles, particularly in the emerging markets, have been deflating rapidly. The flight from risk has broad consequences. By making speculative investments less attractive, it tends to put a damper, for instance, on IPOs and startup funding in general. We saw that yesterday in the way investors dumped the shares of freshly IPO’d Vonage, the internet phone company. We also saw it in the sudden postponement of two IPOs in London. These events, as the Financial Times reports, “demonstrated the growing caution among global investors.” The paper also quotes a Credit Suisse analyst on IPO pricing: “If you are trying to price an issue in the eye of the storm, clearly you will be affected by the current volatility and issuers may need to consider leaving some money on the table.”

No one knows what’s going to happen in coming days and weeks, but it’s fair to say that right now the world’s financial markets are perched on a knife’s edge. Should investors’ flight from risk intensify, it will have momentous consequences, even on little Web 2.0 startups.