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Bitcoin is not so easily manipulated, no one can naked short bitcoins...
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Why not? All depends on what trading rules exchanges follow. If bitcoin ends up as a new asset-class in existing commodities-trading infrastructure, how would that be any different than paper-gold trading?
Blockchain is the ultimate truth teller. Also because large gold holdings are hard to move no one bothers to ask for it. But a large buyer can simply say "transfer my bitcoins here" and the jig is up if nothing shows up in 10 min.