Facebook’s Inc (NASDAQ:FB) already tumbling share prices will come under further pressure as another 804 million shares held by early investors and employees become eligible for sale on Wednesday. It’s the biggest increase in the amount of Facebook shares available for sale since its IPO in May, almost doubling the number of publicly traded shares that currently stands at 921 million, according to a regulatory filing. Investors have already been concerned over the company’s growth prospects.

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The ban on sales was put in place after the social networking site’s initial public offering in May, to prevent the heavy flooding of Facebook Inc (NASDAQ:FB) shares in the market immediately after the IPO. In the last wave of lock-up expirations, many company executives, including COO Sheryl Sandberg had cashed in some of their holdings. Sandberg had sold 353,000 shares for $7.44 million. General counsel Ted Ullyot sold $3.13 million worth of shares. Chief Accounting Officer David Spillane had also cashed in $5.4 million, by selling most of his stake.

The Menlo Park, California-based social networking giant has lost about 48 percent of its value since going public in May. Continued increases in the number of shares put pressure on the prices, and investors are also worried about the company’s ability to generate revenue from mobile advertising.

The company’s CEO, Mark Zuckerberg, is now eligible to sell 504 million of his own shares, which are worth $10 billion. But he has announced plans not to sell his shares until September 2013

Facebook Inc (NASDAQ:FB) shares fell 1.1 percent to $19.86 yesterday in New York trading. However, analysts believe that the new lock up expiration won’t have much impact. Brian Wieser, a senior analyst at Pivotal Research Group, said in a research report, that many shareholders won’t sell as soon as possible, due to the recent decline in stock prices. This one will have a “limited downside.”

During the third quarter, Facebook Inc (NASDAQ:FB) sales jumped 32 percent to $1.26 billion, at the similar growth rate in the second quarter. But, it was lower than 45 percent growth in the first quarter and 55 percent in last year’s fourth quarter. The new ad services showed promising results.

With over 1 billion users, Facebook Inc (NASDAQ:FB) will become a strong advertising platform over time. So, we recommend taking a long-term view rather than being scared by temporary lock-up issues.