Bitcoin holders have spent more than $1 million at Overstock.com since Jan. 9, surpassing the online retailer's expectations and prompting it to keep a stash of the virtual currency that eventually may be used to pay vendors or employees.

Overstock.com Chief Executive Patrick Byrne said the Salt Lake City-based company now expects bitcoin sales to reach $10 million or $15 million this year, up from the $5 million that had been expected. That is a sliver of the $1.3 billion of revenue that the company generated last year.

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