Another day, another low for Groupon's stock. The online deals company issued a lackluster quarterly report after the market closed on Monday. Since Tuesday, the stock has hit a new low every day. It fell another 25 cents, or 5 percent, to close Friday at $4.75. Earlier in the day, it hit $4.51. That's down more than three-quarters of its initial public offering price of $20 in November.