When it comes to strangers, I don't have anything against giving out information that doesn't directly tell who I am or where I am. So stuff like my first name, age, gender and other general information is nothing I wouldn't be comfortable with giving out. Usually I wouldn't have a problem with mentioning my city of residence either, but since I live in a really small town, I honestly don't think that would be the best idea. With friends, I wouldn't mind giving out my phone number either, but that's only provided iMessage is a possibility, since nooot many people I meet online live in the same country as me haha. There are a few people whom I've given my full name to online, but that's only with friends I really trust (fun fact, that happened in an irc channel and ended up being displayed in the random quotes in the stats. watch me scramble to update it before anyone saw). I wouldn't be opposed to giving out my address to said people either, but there's just never really been a reason to though :p
As for teenagers giving out all their information on themselves, I honestly think that could be applied to all ages. You should always be careful with who you disclose what information to, whether you're a 16 year old girl desperate for an online relationship, or someone well into their adult years who's just way too trusting of people. I don't mind people giving out personal information online, as long as it's someone they know they can trust. That doesn't mean this one guy your friend knows, or someone you've been talking to for like a week. But as several cases have proven, people might not always be who they appear to be online, so it's not even certain you can even trust the person you've been friends with for several years D: