Being more open in the age of the computer is not bad or good, it is just different from what people are used to. Remember how parents thought the world was coming to an end with girls scream over the Beatles in the 1960's? The world did not come to an end, and now their music is revered around the world. When people are young they are carefree and do not think about stuff that might make adults pause. With that being said, I have seen people of all ages updating their Facebook page with random facts about shopping, or taking pictures at the beach.
Personally, it does not bother me, and as long as people are not posting extremely intimate details about their lives - who cares really. If you as a parent feel that your kids should not be advertising their comings and goings on Facebook, then cut off the supply! Personally, I think people should be eighteen before they even have a Facebook account, or an online account of any kind. The only thing people under eighteen really need to use the Internet for is research projects, and parents should monitor computer use. Or put a filter on the computer. Do not buy your kids a smart phone where they will be on Facebook all day.