If you were wondering why First Round Capital VC Josh Kopelman has been walking around in a sling, here's your explanation. Embedded, above, is the video Kopelman posted of him breaking his shoulder trying to indoor skydive in Las Vegas. Beware: The mishap occurs around :90 seconds in, and it's totally not for the squeamish. But if you can stand it, it's as good a demonstration of the downside of the Valley's macho, testosterone-driven, thrill-seeking culture as you'll ever need.

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