• by Mark Walsh  @markfwal, August 31, 2012

Even as it taps every ad revenue spigot it can find, Facebook continues to flounder on the stock market. The company's shares closed at a new low Friday after a pair of Wall Street analysts lowered their price targets on its stock, according to a Wall Street Journal report. Facebook shares fell about 5% today to just over $18—more than a 50% fall-off from its IPO price of $38.

Bank of America analyst Justin Post dropped his target on Facebook shares 34% to $23, while Bank of Montreal analyst Daniel Salmon lowered his 40% to $15, the lowest of the 22 analysts with estimates for Facebook. The company's shares most recently took a hit following the expiration of the “lockup” period earlier this month, freeing early investors and company insiders to begin selling shares.

Facebook has rolled out a series of new ad options and initiatives in recent months including expanding mobile advertising, launching a real-time ad exchange, search advertising, and most recently, allowing marketers to target existing customers on the site through contact information like email addresses and phone numbers. Post said in a research note Friday he views the “success of new ad formats as paramount for the stock.”

However, another lockup expiration looms on Oct. 15, potentially resulting in another big sell-off. Post said he doesn't expect to see any “buying momentum” until December.