Treasury Secretary Janet Yellen issued a warning Monday about the dangers that bitcoin poses both to investors and the public. Despite a sharp slide in price to start the week, the cryptocurrency continues to trade above $53,000 as it has received boosts from various sources. Elon Musk’s Tesla recently made a substantial purchase and has said it will accept bitcoin for transactions. However, Yellen said there remain important questions about legitimacy and stability. “I don’t think that bitcoin … is widely used as a transaction mechanism,” she told CNBC’s Andrew Ross Sorkin at the New York Times’ “DealBook” ... (full story)