According to Wikipedia, he also has undertaken a campaign against naked short selling.
Beginning in 2005, Byrne become known for his campaign against naked short selling, a practice which he says has been used in violation of securities law to hurt the price of his and other companies' stock. Under his direction, Overstock.com has filed two lawsuits alleging improper acts by Wall Street firms, a hedge fund, and an independent research firm.
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Byrne was instrumental in Utah's passage of a law aimed at curbing naked short selling. The legislation was repealed in February 2007, after state representatives were advised that it probably would not withstand judicial scrutiny due to federal preemption. Byrne criticized the repeal, but Senate Majority Leader Curtis Bramble said that legal advisers believed that the state would lose any litigation over the law.
Byrne's website has more information about his various actions to obtain justice for himself and others.