The head-turning numbers announced by eBay (EBAY) on Wednesday afternoon certainly gave a boost to the company's stock, and for good reason. The slowdown in growth that had spooked some investors in early- and mid-'06 appears to have been slain, and with $1.72 billion in revenues for the fourth quarter of '06, up a hefty 29% from the same period in '05, there's plenty of reason to cheer if you're long in this stock.

And yet The Browser can't help but feel that there are fundamental conflicts in eBay's business that a good quarter does not resolve. For starters, we're pretty sure that Skype, which eBay bought in 2005 for $2.6 billion, is still losing money. The Form 8-K that eBay filed on Wednesday is not the final word on the fourth quarter, and it doesn't break down the costs of revenue for Skype, so we need to wait for the 10-K that eBay is scheduled to file in a few weeks.

But for the first three quarters of '06, Skype lost about $26 million on about $129 million in revenues. It brought in an additional $66 million in revenues in the fourth quarter, which means it fell short of the over $200 million in '06 revenue that eBay touted at the time of purchase, AND it lost money. So if I were an eBay shareholder, I think I'd still be saying: "Sure, Skype is cool and useful, but did we really have to buy the company? Couldn't we just have partnered with them?" With no obvious path to profitability in sight for a product whose chief feature is that it's free, it remains impossible to see how the Skype acquisition is going to provide return on investment any time in the next decade.

By contrast, PayPal is profitable. But it's not super-profitable. The stubborn fact remains that eBay's "marketplace" business - that is, the buying and selling of stuff online, with which most people associate eBay - is carrying the rest of the company, and left on its own would have profit margins around 40%. Though healthy, the marketplace business keeps running up against roadblocks that threaten the kind of growth eBay's known for. One roadblock is international competition; as Fortune's Adam Lashinsky noted last fall, the South Koreans and the Chinese turn out to have their own ideas about online auctions, and have largely thwarted eBay's considerable attempts to establish primacy in Asia.

Moreover, there's a funny dynamic between eBay and its marketplace users that exists in very few companies. The more eBay needs to grow, the more it squeezes its habitual sellers and potentially drives them into the hands of competitors. One of the most feverish topics in the blogosphere is the fee increases eBay has been imposing on sellers. From the company's point of view, losing marginal sellers who are peddling stuff for $1 might actually be a plus, but alienate enough of them and you make the marketplace less robust and less enticing.

All of which is to say: I think the most overlooked business story of January has been eBay's purchase of StubHub. Meg Whitman et al are no dummies; they recognize that they need to diversify their business to include new profit centers. I'm not savvy enough to know whether the $310 million price tag for StubHub, an online auction site for event tickets, represents a good valuation from eBay's point of view. But I think it's a much smarter investment than Skype, and should help eBay have even better quarters down the line.