The gargantuan amount of high quality user data on Facebook is causing everyone, from marketers to hackers, to salivate like dogs gazing at a steak. They all want a piece of you.

Thanks to Facebook's Open Graph API (which simplifies the development of third-party applications that interoperate with the social networking site) and social plug-ins (which essentially splash Facebook's "Like" button all over the Internet), people who are interested in your data are getting a chance at a much choicer cut of it.

Additionally, Facebook's Instant Personalisation Pilot Programme, which the social network introduced this spring, was the wake-up call for many users who had been ignoring the concerns of privacy watchdogs. In response, Facebook updated its privacy settings in late May, to some praise, and confusion.

Read on to see who's getting a look at what you do on Facebook. You're sharing more than you think, and you might be surprised at what your data is worth.

Facebook Itself

Facebook user dataIt goes without saying that Facebook has unrestricted access to everything you do relating to its site, and its growing collection of profile data, preferences, and connections is prompting some experts to estimate the value of the site beyond the GDP of some countries.

For instance, a Mashable article reported that SharesPost, a marketplace for shares in privately owned companies, suggested an $11.5 billion value for Facebook, versus a $1.4 billion value for Twitter and a $1.3 billion value for LinkedIn.

"You've filled out the biggest survey in the world for Facebook, and you didn't even know it," says Cappy Popp, founder and principal of Thought Labs, whose Doorbell application is one of the top 100 most-used apps on Facebook. "You can't put a price on it because there's never been anything like it," Popp says of the user data that Facebook could accumulate over the next few years.

Everyone Else

Facebook status update displayed on Openbook.comA quick look through the website Openbook, which allows users to search for embarrassing Facebook status updates that anyone can view, shows the volume of people whose accounts are set to broadcast status updates to everyone. Some Facebook status updates reveal far too much.

For instance, a search for "cocaine" or "drunk" in Openbook's search field yields status updates such as "Cocaine is a man's best friend" and "I'm so drunk right now need to go to bed." Note: Despite its resemblance, Openbook is not part of Facebook.

Are these updates just jokes? Are they statements taken out of context? They could be either. But slapped next to a name, gender, and profile picture (information that Facebook requires to be public), they create an impression. And it could cost you.

Just ask Natalie Blanchard, who in November 2009 was fighting to have her health benefits reinstated by her employer's insurance company. The Canadian woman was being treated for depression, but Manulife Financial questioned her health claim after seeing Facebook photos of Blanchard enjoying herself at a party and on the beach.

Facebook's Instant Personalisation Partners

Pandora.com's use of Facebook's Instant Personalization can allow you to see what artists your Facebook friends are enjoying.One day in April, registered users of Pandora and Facebook launched their favorite online radio station on Pandora's site and discovered that they could now see which of their Facebook friends liked the artists and songs they were hearing.

For that to happen, the users either purposely or accidentally passed by the opt-out bar for Facebook's Instant Personalisation Pilot Programme, for which Pandora, Yelp, and Microsoft were launch partners. The same thing happened to readers of MSNBC, who were surprised to find information on stories recommended by their Facebook friends pop up on the news website.

Instant Personalisation allows selected Facebook partner websites to access your data and tailor content to your tastes. With Instant Personalisation activated, your Facebook information is available for access the moment you arrive on partner sites. When the programme launched in April, Facebook automatically activated it for all users. However, a privacy uproar forced the company to revise its policy, and Instant Personalisation is now optional for users.

"A number of people have reported to me that this feels a little weird to them," says Kurt Opsahl, senior staff attorney for the Electronic Frontier Foundation, about Pandora's Instant Personalisation implementation. Pandora declined to be interviewed for this story.