Great article Chris.  Did make me chuckle. 

I constantly attend events as I run my own recruitment business so therefore networking is absolutely necessary.  What I find most frustrating at events, is when somebody knows the person you are talking to, they then move in and join the conversation, but without any introductions made by either party.  Just rude! 

Competitors' blatant intrusion into my conversations can also be very frustrating!  

Oh and when people fail to see that you are having a discreet conversation, and still come over!  You could always argue, there is a time and place!