Shares of Zynga, the principal game site on Facebook, plunged nearly 18 percent after the company posted a huge fourth-quarter loss, its first as a public company.

Shares of the San Francisco-based game developer closed at $11.83, down $2.52, erasing nearly $1.5 billion in market value. Zynga's market capitalization fell to only $8.27 billion.

On Tuesday, Zynga reported a fourth-quarter net loss of $435 million, or $1.22 a share, reversing prior-year net income of $43 million, or 5 cents. Revenue surged 59 percent to $311.2 million.

The developer of games including FarmVille and CityVille said costs rose sharply for research, development and marketing. CEO Mark Pincus said the company increased its users 13 percent to 54 million a day with as many as 153 million each month.

Zynga also reported cash and investments of $1.9 billion, sufficient to fund future development.

Still, Pincus projected full-year revenue to range between $1.35 billion and $1.45 billion, below estimates, with operating income ranging between 24 cents and 28 cents.

The 2012 earnings estimate was essentially the same as for 2011, when full-year operating income was 24 cents.

Zynga, which closed its IPO Dec. 16, has been on a tear for much of the year, especially before Facebook announced its IPO, intended to raise $5 billion, on Feb. 1.

Despite Wednesday's decline, Zynga shares have gained 26 percent. Since the IPO, they've gained 25 percent.