Lock it up... with friends only

Say you are out with some friends and one of your friends (most likely a girl) has brought a new friend with her (most likely a guy).  When they first come in she probably introduces him and he smiles, nods and shakes all the other dudes hands.  I understand that it is good manners to shake hands and introduce myself so I do most of the time, unless there is a huge table between us or I'm in the middle of an intense game of darts, shuffleboard, pool, etc.   

Here is where I get confused.  At the end of the night, or when your friend and her new "boyfriend" leave I will usually shake hands again, say nice to meet you and the like.  But almost always when we shake, the other person wants to lock it up with me or give me the rock too or some other thing that's more than shaking hands.  Usually I break free of these add ons early and pretend that nothing happened.  I mean I just had a few beers with this guy standing around and probably didn't say much to him other than I liked his very fashionable scarf, and now he expects me to lock it up with him like we were college roommates.  Hold the phone!

I may be off on this one but I reserve the lock up, the blow up and the rock for very few close friends.  

So next time you are out and about meeting new people don't be bullied into locking it up, blowing it up or giving the rock to someone you don't know deserves it.  Because if you do there is an uneasy feeling that comes over you like when you stole the tap at that party... don't act like you've never tried to.