I suppose it depends on your circles. Sure if you know someone who knows someone who knows someone... I'm sure if I dug a little through some of my acquaintances (rather than my friends) I probably could get an idea - but it'd be hard to do is subtly. Although I have absolutely no inclination to wanting to and am really not interested in them. However, owing to my gym social circle, I could if I wanted to get my hands on performance enhancing drugs - so I guess you're right, it's who you know. Since i have no interest in that sort of thing I have no friends who are in tune with that sort of thing either.
I really don't "get" it - I get high just going to gym, or eating some nice food, or spending time with loved ones. I think it's a shame that people feel the need to use drugs to take them away from reality.
I've been to Amsterdam many many times, and I've never walked into a coffee shop for "that". It's just not interesting to me.
I've got better things to spend my money on.
Frankly I'm fed up with drugs being a major source of crime - it's just so stupid.