The past two years have been a wild ride for Groupon, and on Wednesday's earnings call the online disount company faces its biggest test to date as investors get their first look at Groupon as a publicly traded company.

Two years ago Groupon was being hailed as the "fastest growing company ever" by Forbes magazine. Google offered $6bn for the firm in December 2010, but Andrew Mason, the company's founder, rejected it.

Last November the firm went public in the biggest, most hyped initial public offering (IPO) since Google. It's now valued at $15bn but, according to critics, the cracks are showing.

Groupon's shares were priced at $20 a piece when the firm went public. Thanks to investor appetite, and the small number of shares sold, they soared to $28 on their first day of trading but have drifted down ever since.

Now operating in 45 countries, the company will report its fourth-quarter results, and analysts expect sales of $473m, up nearly threefold from a year ago. For the full year, Groupon is expected to have revenues of $1.6bn. All big numbers, but profits have been in short supply and with the firm valued at just under $15bn, growth may not be enough to support its current share price.

Rick Summer, an analyst at Morning Star, believes Groupon's shares should be trading closer to $8. "Given the company's phenomenal growth it's understandable people would get excited about the company," he said, adding that the firm was being valued as an internet company when it doesn't make internet profit margins.

Facebook, which filed its own IPO papers last week, recently revealed it had pre-tax operating margins of 47%. Summer calculates that in the long term, Groupon's margins will be in the low single figures. All this as competition increases from coupon competitors, including Google and the Amazon-backed Living Social.

"The only advantage of scale in this business is the ability to stay in business as opposed to going out of business," Summer said.