Facebook likes big numbers - it now has more than 500 million users, each one of whom can have as many as 5,000 friends. Yet as a privately held company, its ownership base must remain small, or it will have to disclose publicly its financial results.

A surging shadow market in the privately held shares of Facebook is making such restraint difficult and could spur the company to go public - even as its executives try to tamp down speculation about an initial public offering - much as similar pressure helped push Microsoft and Google toward their own initial public offerings.

The frenzied trading in Facebook, as well as in Twitter, Zynga and LinkedIn, has caught the eye of the Securities and Exchange Commission. The New York Times DealBook first reported on Tuesday that the agency had asked for information about trading in all four companies.

While it is unclear what exactly the S.E.C. is focusing on, legal experts say that one clear area of inquiry relates to a federal law that establishes a limit for private companies of fewer than 500 shareholders. Once a company has 500 shareholders, it must register its private shares with the S.E.C. and publicly disclose its financial results.

Facebook is well aware of this issue. In 2008, the S.E.C. allowed Facebook to issue restricted stock to employees without having to register the securities, a move that would have required the company to publicly disclose financial information.

U.S. stocks swayed between slender gains and losses on Tuesday as a round of lackluster economic data weighed on the market, but a weaker dollar boosted energy and materials stocks.

The Dow Jones Industrial Average was up 7 points at 11562 in recent trading.

The Nasdaq Composite fell 0.3% to 2660. The Standard & Poor's 500-stock index edged down less than one point to 1257.

The day's cluster of weaker-than-expected data included an index of consumer confidence from the Conference Board, a private research group, that fell to 52.5 in December, below the 57.0 reading expected by economists.

While traders were surprised by the report, some said early holiday shopping figures were a better indication that consumer spending is recovering.

"It appears that there's a disconnect between the consumer confidence index and the reality of what's occurring out there," said Joe Heider, principal at Rehmann, citing encouraging recent retail sales figures.

Still, consumer discretionary stocks slid in the data's wake. Toy-maker Hasbro lost 2.1%, while fast-food company Yum Brands fell 1.1% and Limited Brands, operator of Victoria's Secret and Bath & Body Works, shed 1.2%.

In bleak news for the housing market, the S&P Case-Shiller home-price indexes reported U.S. home prices declined 1.2% in October from September in 10 major metropolitan areas, while the 20-city index fell 1.3%. The 20-city index fell 0.8% from a year earlier, more than the 0.6% decline economists had predicted. Homebuilders slid, including D.R. Horton, off 2.1%, PulteGroup, down 1.9% and Lennar, which fell 0.9%.

In one bright spot, economic activity among manufacturers in the central Atlantic region expanded at a rapid clip this month, according to the Federal Reserve Bank of Richmond. The service sector also showed great improvement.

"The drop in consumer confidence is unexpected and could raise some doubts in the market, but on the other side we're also impressed by the pickup in Richmond index," said Alan Gayle, senior investment strategist at RidgeWorth Investments. "There are clearly a lot of headwinds facing the global recovery but on balance, the U.S. economy should enter 2011 on a fairly good foot."

Trading volume is expected to be light this week and Monday's trading saw the year's lightest volume of any full session. In a week traditionally light due to holiday vacations, the Northeast continued to dig out of a snowstorm that dumped more than 20 inches of snow on New York City. By mid-day on Tuesday, just under 1 billion shares had traded hands in New York Stock Exchange Composite volume. The 2010 average for a full-day sesssion is around 4.8 billion shares.

Metals and mining stocks rebounded after dipping Monday in the wake of China's interest-rate hikes and benefited on Tuesday from a weaker dollar. Titanium Metals gained 2.2%, Newmont Mining climbed 2.7% and United States Steel rose 0.8%.

An unexpected decline in a closely-watched gauge of U.S. consumer confidence weighed on stocks Tuesday even though it did little to dampen expectations that the U.S. economic recovery is picking up steam.

The Conference Board reported that its main consumer confidence index fell to 52.5 in December from an upwardly revised 54.3 the previous month amid ongoing concerns over jobs. The decline was unexpected — the consensus in the markets was for the index to push up to 56.

Though stock markets in both Europe and the U.S. pushed lower following the survey, the response was fairly muted because the it contrasted with the general thrust of recent economic data out of the U.S., especially after the agreement between the Obama administration and the Republicans in Congress to extend due-to-expire tax cuts.

"We expect an uptrend in consumer spirits to remain in place for the foreseeable future," said Joshua Shapiro, chief U.S. economist at MFR Inc.

In Europe, France's CAC-40 was barely a point lower at 3,861.32 while Germany's DAX was around 9 points lower at 6,961.85. British markets were closed for a holiday.

In the U.S., the Dow Jones industrial average was down 7.27 points at 11,547.76 soon after the open while the broader Standard & Poor's 500 index fell less than a point to 1,256.86.

Aside from the state of the U.S. economy, investors continued to evaluate the effects of China's decision over the weekend to raise its key interest rate by a quarter of a percentage point to 5.81 percent — its second increase in just over two months.

Commercial real estate financier Walker & Dunlop Inc. said it has priced its initial public offering at $10 per share, well below the company's expected range.

The offering includes about 10 million shares, including 6.7 million being sold by Walker & Dunlop and another 3.3 million sold by initial shareholders. The company, which is based in Bethesda, Md., had expected to sell its initial shares between $14 and $16 apiece.

Walker & Dunlop has said in previous regulatory filings that it expects to net $89.5 million in proceeds from the offering. It won't receive proceeds from the sale of shares by shareholders. The company plans to use the proceeds to execute its growth strategy, fund working capital needs and for general corporate purposes.

The company has also said that it does not anticipate paying any cash dividends in the foreseeable future.

Walker & Dunlop was founded in 1937 and has grown into one of the biggest originators and sellers of commercial real estate loans, particularly in the apartment buildings segment.

In addition to originating loans for sale to investors or government mortgage finance companies, Walker & Dunlop also services apartment building mortgages and other commercial real estate financing products.

Last year, the company originated more than $2.2 billion in commercial real estate loans, the majority through programs by government-sponsored entities such as Fannie Mae or the Department of Housing and Urban Development.

Real estate investment trust Lexington Realty Trust said Wednesday it is publicly offering $77 million in common stock.

The company is offering 10 million shares at $7.70 apiece, marking a 4.3 percent discount to the stock's closing price of $8.05 on Tuesday.

The company also granted the underwriter a 30-day option to buy up to an additional 1.5 million shares. Barclays Capital is the sole book running manager.

The offering is expected to close on Dec. 20. The company has about 134.7 million shares of common stock outstanding.

Lexington Realty said it would use proceeds to repay debt and for general corporate purposes.

Shares of Lexington Realty rose 6 cents to $8.11 in morning trading on Wednesday.