Investors are buying up Dollar General (NYSE: DG) stock at a feverish pace, hoping to profit from the company's announcement that it will be going private in a $7.3 billion acquisition by Kohlberg Kravis Roberts & Co. (KKR). More than 36.5 million shares traded before lunch Monday at a high of $21.40 per share, representing a 27.5% jump over Friday's close.