Groupon was so hot last year that it turned down a $6 billion acquisition offer from Google (GOOG). Wall Street saw that and eagerly awaited an IPO, figuring that any company that would say no to $6 billion had huge plans in the works.

Unfortunately, it's been downhill for Groupon since then.

This week brings word that Groupon is rethinking its plans for an initial public offering.

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The Wall Street Journal, citing an unnamed source, says that recent stock market volatility is giving Groupon cold feet. Maybe Groupon should be sending flowers and chocolate over to Google headquarters.

Here's how Groupon lost its momentum:

The Super Bowl ad. It seemed like Groupon could do no wrong in the public eye. Then came its Super Bowl spot in which actor Timothy Hutton makes light of human rights violations in Tibet. "But they still whip up an amazing fish curry!" Hutton exclaims at a Tibetan restaurant. Some viewers found the ad offensive.

The competition. Groupon's business model is fairly easy to replicate, as long as you can get a good sales force on the ground to negotiate deals with local businesses. And so a host of competitors has sprung up, from biggies like Living Social and Travelzoo (TZOO) to smaller shops focused on one city or niche.

The burnout. People are getting a little tired of it all, it seems. Vendors say they're sick of the daily calls from Groupon and wannabes trying to make a deal. And customers are overwhelmed by all the offers. After peaking in mid-June, traffic to Groupon and LivingSocial has dropped off, ComScore reports.

The questionable financials. Groupon has some creative accounting tactics, including its use of "adjusted CSOI," or adjusted consolidated segment operating income. But when you approach the financials with common sense, you'll see that Groupon lost $456.3 million last year. The company's marketing costs are astronomical, rising to $263.2 million last year from $4.5 million in 2009. Some speculated that Groupon is dangerously low on cash.

The weird memo. There are strict rules requiring a company to go into a quiet period in the months before its IPO. But during Groupon's quiet period, an employee memo from chief executive Andrew Mason was leaked to the media. The memo defends Groupon's accounting practices and business growth, and it frankly seems written for outside consumption.

The SEC investigation. It didn't take long for the U.S. Securities and Exchange Commission to find out about that memo. The commission contacted a Groupon attorney last week with questions about it, the Journal reports. That quiet period is really supposed to be quiet, you know.

Groupon does not appear to be canceling its IPO. Instead, the Journal reports that it will reassess the timing on a week by week basis. The company has canceled the roadshow it scheduled for next week to sell potential investors on the stock.