This thread is way late. There has been a shitstorm of newfags for almost a month now. I have seen at least ~30 people get an achievement for playing on a server for the first time in the last four to five weeks, I think it's called "Playing Around".
These pricks came from TTT videos about people griefing, ghosting, and dicking around. SNG's been flooded with them lately and there has been a massive spike in temp bans on their end. It's calmed down lately and by referring people to the F1 tutorial and explaining the roles I've had an easier time. Unfortunately there are still plenty of people who just refuse to even listen and just keep killing players.
It ticks me off because A: I have to sit out rounds because I was killed and my killer quit, B: The Traitor may do nothing and I have to wait for the round to Time out out as a dead player, and C: I loose my Traitor rounds.
Fortunately I have other games and it is not the shitstorm it once was.
EDIT: I'd like to say that I have personally asked every player who got that achievement (along with plenty of others) where they heard of Garry's Mod. A large portion of them said youtube. I did not notice any relationship between intentional rule-breakers and new people, but it has been a pain to teach the new people and I get tired of it.