Don't get me wrong, I'm all about including new people and encouraging them to RP, and/or RP'ing with them if they just do it naturally. I would certainly share a drink and conversation with an unknown character. I've been in a couple of instances though, where things get bad fast, and you have trouble pulling away. When you finally do, you kind of have to disregard however much time you went along with it, and that just sucks.
Again, I'm definitely not saying exclude new people...just be cautious when engaging in anything other than light RP. I hate having to say "OK, that last hour doesn't count, these things never happened..."