I'd love to see a single "facilitated drug transaction" in /r/trees. No really, it would be relevant to my interests. Also, it's a load of nonsense, as are most of the comments about /r/trees, /r/atheism and other subreddits that are being compared to CP in this thread.
It was one cautious commenter away from being a thread all about where to meet up to do and buy illegal drugs. You think that just because you say "share" with a wink and a nod everyone's immune from prosecution?
So a 2 month old post (that wasn't even in /r/trees) whose TOP comment says specifically "do not talk about actual trading of drugs" is your evidence that /r/trees is illegal? Besides, there's nothing inherently illegal about me claiming "I sell lots of drugs". Yes, it's (not) true, drivebyacct2 sells massive amounts of marijuana. Come persecute me and everyone else in this thread!
Even the second comment is how to be safe and not attract too much attention. The third top comment suggests that it be a "treeless" meetup.
In the interest of fairness, I've never been to /r/nyctrees before and it's certainly a different style than trees. I'm still not sure anything there looks like dealing and again, I don't really see "hey, let's get high and meetup in [some] park" as being that dangerous or scandalous.