In my ongoing need to justify whey I’m not on Facebook, I have a couple of quotes that aptly explain some of the reasons:

Social-networking sites present a different kind of problem. Facebook, LinkedIn, Friendster and others typically provide value by capturing information as you enter it: your birthday, your e-mail address, your likes, and links indicating who is friends with whom and who is in which photograph. The sites assemble these bits of data into brilliant databases and reuse the information to provide value-added service—but only within their sites. Once you enter your data into one of these services, you cannot easily use them on another site.

And,

Your social-networking site becomes a central platform—a closed silo of content, and one that does not give you full control over your information in it. The more this kind of architecture gains widespread use, the more the Web becomes fragmented, and the less we enjoy a single, universal information space.

Who said that? Tim Berners-Lee. I’m not saying that we should make all of our personal details available on the web, but what I do think is that using our personal information as a currency for advertisers is not good. It is inevitable that such data has to be kept behind a walled garden, which is entirely against the core principles of the web.