R.D.
I actually feel really bad about this because I said this to a girl who was totally shy and kind of latched onto me because I was the only person who would talk to her, but I finally interrupted one of her rants and said 'OMG do you write a blog?! No?! I think you should... I think you should start RIGHT NOW'... and I walked away.
Yeah, don't do that. Totally rude. I just felt trapped at the time and didn't know what else to do! You could always say something like 'I'm sorry to interrupt, but I've really got to go to the bathroom/ call my mom/ pick up a friend/....