What evidence do you have to support this?
How private do you think it is?
What kind of information do you intend to put on Facebook?
I'm in a career change from technology to nursing. A trend I've noticed about how folks interact with various internet entities (like facebook) is that many either over or under react.
Folks who under-react don't consider the need for security/privacy controls at all. As a result, they may find themselves in a tough spot.
Folks who over-react, tend to see goblins behind every corner and often just decide to not join any online entity.
The reality (as is often the case) is somewhere in the middle. Just as we all had to learn how to keep ourselves safe in the real world (look both ways before crossing streets, lock doors, don't walk at night in badly lit areas, don't flash cash on the street, etc)....we need to learn to keep ourselves safe in the virtual world (never put sensitive information in e-mails, don't share with people you don't know, don't download files you're not expecting, etc).
Now, we can decide to become virtual recluses just as we can choose to merely lock ourselves in the house (it does decreases risk)...or we can manage our risk and still participate.