It's just one disappointment after another for Groupon (GRPN) shareholders. The stock hit a new low Friday, and closed down more than 4% to $8.44.

Groupon is now 58% below its November IPO price. This is a bloodbath. Shareholders have lost all faith in the company.

The latest hit to the stock was a blog posting by chairman Eric Lefkofsky, who said he's going to turn his focus to his venture-capital firm, called Lightbank. The implication here is that Groupon's young CEO, Andrew Mason, will assume more of the management reins.

"I look forward to continuing to work with Andrew in my ongoing role as chairman of the board," Lefkofsky wrote, "but in the meantime, I've immersed myself in Lightbank and am focused on growing the company."

Lefkofsky is continuing as chairman, but shareholders are concerned that he is mentally checking out. And Mason, who is in his early 30s and drinks beer at employee town hall meetings, isn't trusted enough to handle all the added responsibility that may bring.

Groupon continues to deal with the threat of deep-pocketed rivals crushing its business model. Amazon (AMZN), Microsoft (MSFT), Google (GOOG) and others are making a play in the daily-deals business