It has been happening alot lately and I think it is a little rude even though it is only a few that do this.  When you enter a channel with other members in it please say you entered.  And the worst is when you leave.  Don't just exit without a word.  I can understand if you lost a connection, but if you are through playing for the time, just say so.  This is suppose to be a bunch of friends playing together.  I would never walk away from one of my friends I have been talking to and leave without a word.  Its not that hard to say I'm out for the night.  Also, whats with all the "hit & runs", (entering the lobby and exiting in one second)  If you are looking for someone, fine.  Just say hello to whom ever is there and then leave or ask if you have seen this person.  Get an answer and then go.  This shouldn't even be rules, just common courtesy.

I'll sometimes join and go in the channel and play for a while, then I'll have to answer the phone or something will come up unexpectedly and I gotta run, so I've probably added to what you've been noticing.  But we have the teamspeak channel up on the website, you can see who is in it or who isn't.  I don't see any reason why people have to look for specific people, everyone in UGC is awesome, I wanna log on just to say hi to whoever is in there.  But yeah, that resource is available if you'd like.

Just my two cents.