Despite the promise of more money flowing in, investors can't take their minds off eBay's ( EBAY) other worries for long.

Indeed, the enthusiasm triggered by eBay's fee increases seemed to dampen just one day after the auction giant announced them.

Shares of eBay closed Friday off 81 cents, or 2.6%, to $30.78. The pullback followed a gain of about 4% on Thursday, when the company said that it would introduce a slew of new fee increases for its auction services.

Kicking off the new year with fee increases has become routine for eBay. "An important part of any business strategy is a regular evaluation of our pricing structure," eBay North America President Bill Cobb wrote on the company's blog. Usually, "we make changes on an annual basis at the beginning of the year," he wrote.

Some analysts saw the latest round of fee hikes as a bullish sign that eBay didn't need drastic measures to take further advantage of its slowing core auction business. The fee increase is "consistent with our view that eBay continues to have some (modest) pricing power and is the preferred action versus more bearish case of eBay needing to lower fees to maintain listings growth," wrote Merrill Lynch analyst Justin Post in a research note on Friday.

Post also wrote that sellers will pass on a portion of the higher fees they are paying by charging buyers slightly more. Merrill Lynch makes a market in eBay shares.

The company's latest move comes on the heels of an announcement in December that it would begin charging for a portion of the Internet phone service offered by its Skype division.

While both of these moves will help eBay bring in more revenue, investors will likely keep an eye on some big question marks before really getting behind the stock, which has dropped about 10% from a mid-November high.

Among the biggest concerns are eBay's recent setbacks in international markets. In December, eBay announced it would scrap its own Web site in China in favor of playing minority partner to the locally based Tom Group. eBay is facing slowing growth in South Korea, where it faces stiff competition from local companies such as Gmarket.

And eBay's growth in Germany seems to be stumbling compared with its earlier performance. Core listing growth was up only 4% in the fourth quarter of 2006 as compared with 34% for the third quarter and 47% for the year-ago quarter, estimates RBC Capital Markets analyst Jordan Rohan in a research note.

Rohan also wrote that eBay also will likely aface increasing competition from Google's ( GOOG) recently launched Checkout service. Heavily promoted by the search giant, Google Checkout allows users to make purchases from online merchants -- directly competing with eBay's popular PayPal service. RBC Capital Markets makes a market in eBay shares.

Given the new challenges, it's going to take more than the usual boost in fees to lock in investors for a longer haul.