When it comes to privacy, the pendulum has swung dramatically over the past 20 years.

It has gone from a world in which only friends and family (and the government) knew your personal details to a point in which millions of people happily disclose public information on social media services such as Facebook, Twitter and LinkedIn.

The willingness to talk about everything and anything has jump-started the growth and interest in social media by making it a dynamic, engaging, informative and data-rich environment for users and, as important, marketers and advertisers.

When you have in-depth knowledge of consumers, there’s no lack of possibilities or opportunities to capitalize on it.

But there is an elephant in the room. A growing concern about online privacy, sparked by Facebook’s latest efforts to leverage the personal information of its 500 million users to deliver more relevant advertising.

It has sparked a renewed discussions about the information collected by online companies, including major players such as Facebook, Twitter, Google and Yahoo!

Suddenly, a growing number of consumers who were oblivious to how much information they disclosed are looking at what they are saying online, and how that information is being used. In many regards, it has been a wake-up call after years of being asleep at the privacy wheel.

With the pendulum maybe starting to swing away from total disclosure, the question is whether growing concerns about privacy will take the zing out of social media. If people are less enthusiastic about publicly revealing a wealth of personal information, does that make social media less interesting, including to advertisers who have been gorging at the full-disclosure buffet?

Given the current behaviour of consumers, it would be extreme to suggest that privacy concerns will kill social media but they could make social media a less interesting landscape.

If companies such as Facebook have to provide consumers with more control over how their personal data is used, does it make these services less compelling to advertisers? If that happens, does social media becoming less viable as a business opportunity?

What do you think? Will privacy kill the social media “golden goose”?

More: For another interesting take on the privacy issue, here’s an interesting article in the New York Times about Bynamite, a start-up that gives users more control over the personal information they disclose.