Oh man, I learned that the hard way. I had gotten into Cannibal Corpse recently (only about a month ago), and one time while I was bored in class, I decided to look at some CC lyrics... It took me a minute to realize that a few curious (and probably disturbed) classmates were reading what's on my screen.
It's definitely not for the faint of heart. My friend and I were talking about the band during class, and my teacher was like, "You guys like Cannibal Corpse? I could never get into their music..." Wonder why, lol.