Uh-oh. Just after Groupon (NYSE: GRPN) confessed that it hadn't exactly gotten its recent accounting right, the SEC announced it would be nosing around the company's finances. Groupon's "errors" compelled the firm to restate its results downward by tens of millions of dollars. Predictably, the shares tanked on this ugly news. This didn't help the reputation of the market's recent crop of IPOs, of which Groupon was a charter member. But fear not, there are better new firms with sturdier business models to invest in.

Revenue on a sharp rise
Groupon made a splash when it first launched online, as its business model was fresh and compelling at the time. Every day it featured deep bargains from local firms. Where else could you get that many free donuts or 50% off a flying lesson? Accordingly, revenue took off quickly like...well, a low-cost flying lesson, zooming from $14.5 million to $312.9 million to $1.6 billion from 2009 to 2011.

Profitability was and remains elusive, but such are the ways of young and fast-growing companies. Groupon was and is a hit, to the point where the company name has almost become a common noun for "getting a nice deal on the Internet before it expires." It's inevitable that it'll start turning a profit at some point, right?

No fences here
Er, probably not. The one hole difficult to plug in such a business model is the near-total lack of barriers to entry. It's a fairly simple matter for a company to ink deals with local and national vendors to offer Groupon-style deals.

This is already happening with some big Web names that don't want to be left out of the party. Not long ago Amazon (Nasdaq: AMZN) begat its Local sites, which have reliably cranked out deals-of-the-day that are easily the equal of Groupon. The same goes for Google's (Nasdaq: GOOG) Offers suite of websites.

The advantage an Amazon or a Google has is that it can point toward those deals while users are surfing one of their sites. A Google search or an Amazon buy can lead to the purchase of a coupon, given clever ad placement nearby on the page. Meanwhile, smaller players like privately held LivingSocial are also slinging coupons, further eroding Groupon's market share and ramping up competition.

There are prettier guests at this soiree
Companies new to the market are always inherently attractive, as they're freshly infused with cash and usually on a sharp upward revenue trajectory. Fortunately, there has been a pile of IPOs in recent months to choose from, and there will be even more in the wake of Facebook's upcoming debut.

Many of these are a lot more appealing than Groupon. For example, Proto Labs (NYSE: PRLB) has a unique business model centered on producing molded plastic parts on demand and delivering them quickly to customers. Revenue is growing, and the company is profitable. And unlike our troubled Groupon, its barriers to entry are formidably high -- after all, it's pretty hard to HTML-code an injection molding machine. Also in contrast to Groupon, Proto Labs sits well above its IPO price at just over $35, compared with $16 at issue.

More famously, shares of business networking site LinkedIn (NYSE: LNKD) have blown past reasonable expectations, rising 128% to $102.64 from their debut at $45. Although the company is fairly one-dimensional and its stock has a scary forward P/E of 163, LinkedIn has been moderately profitable of late and boasts a wide user base, so investors have some basis for investing in it.

Another plus for both companies is that neither has restated its earnings or been the subject of an SEC probe in its young life, unlike certain other recent IPOs we could name. So look for both to continue doing well in terms of share price -- though here we'd have to give the edge to Proto Labs, as its fundamentals are stronger, its business model more compelling, and its stock not as "discovered" (i.e., pumped up in price) as LinkedIn.

While Groupon's business model gives me pause in a big way, The Motley Fool recently uncovered a stock it thinks has outsized potential for investors -- so much so that we named it our top stock for 2012. You can read all about it in a free research report, courtesy of The Fool. Just click here to access your free copy today.