Feb 28, 2013 · 3 minutes

Andrew Mason has his own kind of panache. Not the epic, Steve Jobs panache. Or the eclectic, Barry Diller panache. Or even the oafish, Steve Ballmer panache. But as a CEO of one of the fastest-growing startups in history, he had the small-scale, misfit quirkiness of an indie movie. Panache-ette.

Looking back on Groupon's meteoric history under his leadership, Mason's offbeat style was at once one of the best things and one of the worst things about the company. It put a playful, giddy spin on its daily deals business. But it also sounded a harsh note on Wall Street and sometimes veered into the bizarre. Mason exemplified the cult of the founder even as he outlined its limitations.

Now the Mason effect is gone from Groupon, along with Mason himself. “I've decided that I'd like to spend more time with my family. Just kidding -- I was fired today,” Mason wrote in a goodbye memo signed, “Love, Andrew.” It was pure Andrew Mason. Endearingly honest, yet unintentionally awkward.

Mason seems to be departing with his sense of humor intact. By the same token, his departure is unlikely to change anything at Groupon. He was, at most, a symptom of a deeper problem, the cherubic face of a young company that was growing up too fast. Groupon is still going to have to deal with the hangover of growing too much too quickly.

The defenestration of Andrew Mason was widely expected, telegraphed in recent months by rumors that the board was looking for someone more seasoned, and made all but certain after a dismal earnings report yesterday that sent Groupon's stock tumbling 24 percent today. (The stock spiked 12 percent briefly in after-hours trading on news of Mason's departure, but fell back. It's lately trading at $4.70, up 4 percent from the official close.)

In what must have been a gesture by the board to show it was serious, Mason was sent packing without a new CEO in place. Instead two board members, executive chairman Eric Lefkofsky and vice chairman Ted Leonsis, will be interim co-CEOs. But this move is in itself unsettling. Co-CEOs rarely make for a good solution. And interim leaders will only add to the uncertainty that is weighing on Groupon's stock.

What's more, Lefkofsky's influence on Groupon during its rise is greater than it appeared while Mason was at the helm. The grow-at-all-costs ethic that spurred Groupon's early success and is causing its present problems is right out of the Lefkofsky playbook. Lefkofsky was one of the Groupon insiders who cashed out hundreds of millions of dollars before the company's IPO.

Lefkofsky still owns a fifth of Groupon shares, however, so he still has a vested interest in seeing the company succeed. And for now, he and the board have bought at no cost something they very much need: more time. Swapping CEOs can cause turmoil in the short run, but it allows you to beseech unhappy shareholders to give the new CEO at least several quarters to fix things.

That new CEO will have a tough task. Groupon's main business – the daily-deal, group coupons – rode a consumer fad that grew popular before losing allure as quickly as eBay's auctions did a decade ago. The newer Groupon Goods, which sells discounted products directly to consumers, is a low-margin business that could easily be undercut by other competitors and that is already seeing its annual growth slow down.

Groupon could well find modest success in these areas over time, but it's quite likely that its days of rapid growth are coming to an end. It's hitting middle age sooner than even a lot of Internet startups do.

In that sense, the departure of Mason's youthful face is fitting. Perhaps a more weathered, world-weary appearance is needed to set the tone for the company's future expectations. But a word of warning to that new face: Stay away from the window in the CEO's office. It's a dangerous place to stand for too long.