It's only dangerous if you're daft enough to divulge information of a sensitive nature. I'd wager most of us aren't exactly new to this game, I've been using the internet and various forums, message boards, social media and so on for over 20 years. In all that time I have been compromised precisely 0 times.
I have no problem talking about a wide variety of things, personal or otherwise. But there is a line that any sensible person draws as to what information gets to cross it. If you stay behind that line the worst that can happen is someone, somewhere knows a little bit about you. Which would still be far less than say, a casual acquaintance would know.