I work in Europe for a computing American Corporate (Nasdaq). They have a Facebook page where they have photos/profiles of employees. They encourage employees to share their facebook pages, and a lot of them like to show where they were last weekend with their snotty babies and friends(!). Unfortunately, even in computing, a lot of people are ignorant in relation to privacy, or choose not to care, as long as they look good with upper management...
OTOH, I have 3 sisters that have non computer related jobs and it's a battle to explain this exact issue here in /. because they too are so naive that fear nothing from their "harmless activities". (As happened to a friend, someone recognized some friends in photos that is a known [pick one - communist, gay, black, pot smoker, etc, bla] and he was stalked for some time...
I lost contact with some friends because they don't look at their emails anymore, but are on facebook every day. I even considered opening a fake account just to contact them, but I too will not bother...
I have never had a facebook/tweeter/myspace/bla,bla account and never will, but I'm a computer programmer...