After all the buildup, Facebook's long-anticipated initial public offering is finally here. Facebook stock is set to begin trading with the stock symbol FB on the Nasdaq Stock Market at 11 a.m. ET. That means Wall Street will have an hour and a half after the market normally opens at 9:30 to prepare for what is expected to be a deluge of Facebook-centered trading activity today. See a livestream of the Facebook launch at Nasdaq.

"Having Facebook operating as a public company is very important in terms of really gauging the role of social media," said Ezra Gottheil, an analyst with Technology Business Research. "We will really get to see how Facebook, the dominant social medium, is performing. How much money they can earn is a reflection of their value in the economic world."

On Thursday, Facebook set its initial share price at $38. With the company offering 421 million shares, it could raise upwards of $18.5 billion in its IPO .

The company now has a valuation of about $104 billion.

Facebook employees welcomed the IPO with an all-night hackathon last night in its Menlo Park, Calif., offices, the BBC reported.

While the IPO is an important milestone for Facebook and its 28-year-old co-founder and CEO Mark Zuckerberg, it's also a bellwether for the entire social networking world.

Facebook is the largest social network in the world, with about 900 million active monthly users. According to Experian Hitwise, Facebook became the top-ranked Web site in the U.S. in March 2010. One in every five page views in the U.S. is on Facebook.

If Facebook's IPO is wildly successful, other social networks, such as Twitter, are likely to gain with more investor backing. However, if investors aren't as eager as expected to buy Facebook shares, or if they buy shares and the price drops in the coming months, the likelihood of IPOs from other social networks companies becomes more tenuous.

Today's top stories

Steve Jobs worked closely on design overhaul for iPhone 5
Apple board member: Steve Jobs wanted to build the iCar
Sorkin reveals plans for Steve Jobs movie, Woz hired as tutor
Get £100 off new Macs in Apple scheme, 17 June end suggests new launch
Apple patent points to Retina display Macs – report??
Apple lets Jailbreak back into App Store, iTunes Store
Conmen replace iPhones, laptops with Coke and spuds
Judge tells Apple and HTC to talk settlements
Kodak says Apple attempting to buy patents 'on the cheap'
Renewable sources will power Apple's data centre by 2013
Loss of Apple chip contract sees Samsung value decline