Once upon a time when people came together it was likely to be in a civic space – a common, park or town hall. Then came the shopping malls, which provided air conditioned meeting places, so long as you didn’t mind being bombarded with commercial messages.

Now we have social networking online, and after announcements over the last week, those who have been hanging out on Facebook and MySpace have to confront the fact that all the information they have been swapping with friends – where they go, what they like, what they worry about, what music they listen to, what they just bought, and possibly their intimate experiences and thoughts – is a commodity up for sale.

Facebook and MySpace are both selling the information provided by their users to allow advertisers to better target the ads. You can see the Facebook pitch here, and here’s how the advertising trade publication B&T reported the MySpace moves earlier this month.

The new tools provided to advertisers by these sites go well beyond normal demographic targeting. They slice and dice the audience by interests. Just how finely diced that is only the insiders know, but the potential to capitalise on the (not so) secret thoughts and intimacies of a largely young audience is obvious.

Is this a privacy concern? Crikey contacted the office of the Federal Privacy Commissioner, Karen Curtis, about the issue this morning. The response indicates that it is really up to the site users to protect themselves.

Users should read the terms and conditions carefully, says Curtis, including whether their personal information can be sold.

“Given the ubiquitous nature of the Internet, its users need to take special care to understand their rights and ensure that the privacy of their online personal information remains secure.”

The social networking sites are, after all, public spaces, as the conditions of use make brutally clear. Facebook reserves the right to release the information that users provide (including favorite movies, television shows, books, music and so forth) to organisations.

It’s just that people have to remember that all that cosy chat and connection is taking place not in civic space, but in the middle of a shopping mall – and the spruikers are listening in.