One of the biggest buzz kills for me is not having anything to do. You've just finished smoking all the weed, and then nobody can think of anything fun to do or even anyone's house to chill at for a while...
It's like, "What do you want to do man?"
"Oh, I don't know, what do YOU want to do?"
"I can't think of anything, I think I'll just go home."
That's one of the reasons I've cut back on smoking, it's like it somehow eventually LEADS to boredom sooner or later. That's why I try to plan something before smoking, so that smoking doesn't end up becoming the activity for the night.