Berkshire Hathaway CEO Warren Buffett has argued against borrowing money to invest in stocks.But that's exactly what investors are doing in record numbers. Margin-debt balances — loans individual investors take from their brokers in hopes of beefing up their portfolios and maximizing returns — rose to a record $665.72 billion in January, according to data from the Financial Industry Regulatory Authority. Buffet says, "Borrowing money is a way of trying to get rich a little faster, but there are plenty of good ways to get rich slowly."