I can't tell you how many times I've sat next to someone at a table during a conference or workshop and a person on one side or both will turn their backs to me. They want to talk to their friend and no one else. They'll glance at you and quickly decide you're no one important.
Well, all I can say is be careful if you do that. A few years ago, a woman sat next to me at a conference who looked like any regular overweight, middle age writer a person can find (like me). Nothing special looking (like me). At first, she was a little quiet, but a new friend (made at that conference) and I started talking to her. Turned out she was the late Kate Duffy. Yes. The famous Kensington editor who helped romance novels to become what they are today. Click on her name to find out about her if you don't already know.
She was wonderful, friendly and oh, so kind. I had so wanted to work with her. (Though I have to say I love working with my Avon Impulse editor. She's wonderful, kind and smart. Yes. I'm a little bias. She did pick me out of the slush pile.)
So next time you sit next to someone at a writers' function, be nice, friendly. It may pay off. They may even be someone important or someone you will later be happy to say you know personally.