Originally rising to prominence as one of the darlings of the original tech bubble, eBay (NASDAQ:EBAY) proved last year that its days of generating massive returns for shareholders are far from behind it. However, the eBay of today looks barely recognizable compared with its original online auction business model, and in a good way. Thanks to a set of savvy business decisions, eBay has refashioned itself into an e-commerce powerhouse to rival online megastore Amazon.com.

However, after putting up some amazing numbers in 2012, does eBay still what it takes to keep investors happy? The Fool recently created a premium research report that breaks down in clear detail each facet of eBay's online empire. To help inform our readers, we've included a brief excerpt from this report. Read on, and enjoy!

One of the primary risks at eBay at this point is valuation.

By mid-November, eBay was a still steep 18 times the projected profitability for all of 2013. An earnings multiple in the high teens may not seem outlandish, but it still represents a slight premium to eBay's most recent growth.

There's also a somewhat troubling metric. Return on invested captial -- on a trailing-12-month basis --peaked at 25.7% during the first quarter of 2011. The metric went on to decline for five consecutive quarters before stabilizing during the third quarter of 2012.

eBay's two marquee businesses also have their unique threats.

For PayPal, it's not just the fear that growth rates may start to decelerate. With merchant services climbing 26% over the past year, it's not as if PayPal's hearty upticks are sustainable. Investors get that. The real concern here is that the disruptor may be disrupted.

Just as PayPal's real-world initiatives are starting to eat into the success of credit and debit card issuers and marketers, the tables can also turn on PayPal. Visa, for example, now has V.me as a digital wallet service.

There are also other companies making a run at merchant services. Square has been a hit with small businesses looking to shave the hefty transaction costs of processing traditional plastic, but now even Groupon is throwing its hat into this ring with cutthroat deals. Competition will drive down transaction rates. That's good for merchants and perhaps consumers, but it won't end so well for the payment platforms.

For eBay's marketplaces, challenges come with the territory.

eBay has been able to flick off potential disruptors with ease. When rival auction sites tried to make a dent by offering low or no listing fees and rates a dozen years ago, merchants still found themselves flocking to eBay because that's where the buyers were.

eBay also survived the Craigslist threat a few years later. There's something to be said about the nature of a proven platform with established feedback ratings to grade sellers.

However, as eBay morphs into a more traditional online retailer it will face stiffer competition. The transformation is taking place. Auction listings have actually fallen through each of the first three quarters of 2012. There are seasonal considerations, but keep in mind that fixed price auctions have shown back-to-back quarters of sequential gains.

There are also new ventures that can backfire.

Bill Me Later, the company's fast-growing platform for purchase finance, is growing quickly. With total payment volume of $775 million during the third quarter, we're looking at a 37% pop over the past year. What happens if the economy retreats, and more borrowers default? Right now, eBay is generating a welcome 16.5% risk-adjusted margin through Bill Me Later, but this can turn with the economy.

GSI -- the e-commerce services provider that eBay acquired and makes up the balance of the company's revenue outside of marketplaces and PayPal -- is generating segment operating margins of 6.1%. That's a lot leaner than eBay's larger businesses, and the top-line growth at GSI hasn't been all that impressive lately.

Yes, eBay investors. As consistent as the company has been, there are real risks.