The closest thing that I've had to do was back in high school some kid went retard in one of my classes and me and 4 other students from the class had to go and write up summaries of the incident.
I didn't omit anything, even though I had no real issue with the kid, just laid it out like it went down. He started yelling at the teacher, calling her and her assignments dumb in a variety of ways and using colourful language.
He got expelled as a result.
That's the closest I ever got to "snitchin'"
Not too long ago, several months ago, this guy I know overdosed on a bad batch of boy and when EMS came to take the body away the cops made his brother get in contact with the dealer to try and get to the source. Whether or not that panned out for the police in the end, I have no idea. I hope they caught up with whoever was running that particular racket though. Unfortunately taking one deadly batch off the streets is just a drop in the bucket in the larger scheme of things but at least they're trying. A lot of law enforcement types really don't hate drug users and feel pity for them. The law is the law though, and they'll arrest you if you get caught. But they don't want deadly drugs being peddled. It strains their resources and cuts short the lives of many innocent people who were unfortunate victims of circumstance.