The iShares Semiconductor ETF just delivered a "historic 34% surge" in 13 days, and that should terrify you. When CNBC breaks out the "historic" label and retail investors start salivating, smart money is already heading for the exits. Take $MU at — sure, they're pulling in revenue, but the market is pricing these companies like they've repealed the laws of cyclical physics. Spoiler alert: they haven't.

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