New York | Mark Spiegel begins some mornings contemplating Tesla's fate from the bathroom of his high-rise apartment, where two computer screens are perched near the bathtub for instant updates on his Twitter feed and stock prices.

The hedge fund manager spends much of his day at his dining room table, where he fires off tweets explaining his high-stakes bet that Tesla, a darling of Silicon Valley and a $US60 billion ($82 billion) behemoth, will eventually fail, sending its stock price tumbling.