The following was initially a comment on danah boyd's recent post discussing Facebook's "slippery slope" of betraying its users, most recently with Project Beacon. Please share your thoughts if you have them!
"Trusting Facebook users" are generally older folk- I think they're more open to publicizing their online profiles because they're seeking to make connections, they're gaining from the public exposure and excited by all the novel possibilities. My ethnography of social networking sites primarily re/presents the voices of college students- particularly veteran Facebook users. The site started out as being a great little niche environment, so people could exchange intimate messages and upload photos from that crazy party where everyone was on a ton of drugs and so on. Then it opened up, everyone was pissed, and that's when attitudes toward Facebook started to shift.
Most first-generation Facebookers have some degree of distrust/disgust for the site, often a great deal of it. Yet they continue to use it because it's become so firmly integrated into campus social life- it's a way to easily invite people to parties and share photos from said parties, to visually organize one's social network and keep track of alumni and old high school buddies, to find out the sexuality or relationship status of that boy you've been admiring from afar. It's crucial. If you're not on Facebook, you're going to be somewhat out of the loop.
Such important social practices generally take precedence over the egregious invasions of privacy that most are highly suspicious of. The trend is not abandoning Facebook- it's far too useful. However, the site's reputation is definitely tainted, and some Facebookers are using the site to form or join groups that promote awareness of Facebook's privacy policies and petition for change. Most, however, are simply becoming more savvy and protective of their online personas; it's become increasingly common for me to be unable to access the profiles of those I'm not friends with because of that practice. Others have simply taken to deleting much of their profiles, leaving just an e-mail address, a witty or ironic comment, and maybe a funny picture. There's also a huge trend to apathetically accept that nothing can be done about it, much like how a lot of young people feel about our government.
Again, these are just observations of the changing attitudes among a specific subset of Facebook users. They know what's going on (though I would say that only the Tech-savvy blog-readers have even heard about Project Beacon- but they know their information is being used for capitalist endeavors), they're disgruntled that so much of what they do on Facebook is publicly broadcast and forever archived. Regardless of how they talk about it, however, they're still using it regularly for everyday social practices. For many, it's become as habitual to check Facebook as it is to check e-mail.