Privacy isn't very important for me, but I recognize the negative effects sharing too much online can have. This article from The Globe and Mail talks about how sharing too much on Facebook can make it easier for criminals to conduct fraudulent activities.
It reminds me of an experience I had back in high school, my friends and I played a prank on another friend who had a bad habit of falling in love with people online. We made a fake persona for him to fall in love with as sort of an intervention. He, as we expected, fell in love with the 'girl' (who was ironically controlled by another girl he used to have a crush on). It was really mean, I kind of regret it now, but at least he took it well and laughs about it now.
That experience also taught me a lesson. Now, I don't take any thing I see online that seriously. Anybody who messages me could be another person controlling that person's account. For any deep, serious conversations that could potentially be embarrassing I usually prefer voice chat or video chat.
This article proves my point. The article mentions a sex offender that posed as highschool girls in order to get guys to send embarrassing pictures to them. The sex offender would then blackmail these guys for sexual favours.
When I think of privacy online, I usually think in terms of employment. Will posting this picture make it harder for me to get a job? I try to pretend I'm a recruiter and look at my own public profile to make sure nothing is too nasty out there. That being said, I feel I have a pretty balanced online life. Some people go all out and deactivate Facebook, but they really miss out on Facebook's ability to plan events and to allow people to share experiences with each other. It seems like that using services such as Facebook is a trade off between convenience and privacy.