It's funny that this topic is posted in a drug discussion forum.....*rolls eyes*
I get what you mean about people that only talk about drugs though, it is especially annoying when you're not on drugs and want to be, or when you have friends over who don't take drugs and get really bored by the conversation....
I think sometimes it's a bit of a dick-size competition, comparing notes etc...
as for myths etc, well i don't really hear a lot about that as I tend to assosicate with people who are better educated about drugs, but I personally like the occasions when i meet someone who doesn't know much and has all these questions that i can answer with facts instead of media-hyped lies.... then i don't mind talking about drugs... What it hate is the recapping of "that night we smoked a G in 2 hours" conversations that you've heard a thousand times, that really serve no purpose or the "those were the best pills of 06" conversations, or, my personal least-favourite "omg i'm so high right now"... grrr! you don't take drugs to talk about being on drugs!!!
But, sometimes people don't have any life-changing ideas or eppifanys on their mind, and silence needs to be filled in that weak pea-soup coloured part of the morning when you don't quite want to wrap up your good time just yet but your mind is a little broken from talking philosopy all night....
The tried and tested solution is to tell the offending party that their story sucks and give them a new topic... people may get offended at first, but they soon realise it's in their best interest to shut up.... but you'd better have something else to talk about, because otherwise you get that eery silence that means the party is over and you have to start putting pieces back together... better to ramble about boring things until a real conversation starts then sit in uncomfortable silence realising that you haven't eaten for 2 days, your house is a mess and somehow you have to work tomorrow....