JPMorgan Chase, Bank of America & Citi bar people from buying bitcoin with a credit card

*Bitcoin's rapid tumble from December records comes amid a slew of negative news for the the cryptocurrency world.
*J.P. Morgan Chase, Bank of America and Citigroup said Friday they decided not to allow customers to buy cryptocurrencies with the companies' credit cards.
Reports last week increased worries about potential price manipulation at one of the largest cryptocurrency exchanges in the world, while regulators around the world are stepping up their efforts to limit speculation.