Facebook’s first-half revenue roughly doubled to $1.6 billionsocial network’s appeal to advertisers.

Net income in the first half of 2011 came to almost $500 million, according to a source, who wished to remain anonymous because privately held Facebook does not disclose its results.

Facebook’s strengthening results come as investors have pushed the company’s valuation to roughly $80 billion in secondary markets, with many industry observers expecting the company to go public in 2012.