I was thinking about this today at Market. Granted you are there to sell your product, but there will be downtime and the person you are next to can either make things a lot more fun or drive you nuts!
The things that make me nuts are people that "hawk" even though it's not really allowed ' - "have a sample of pie, it's good for you...ish". It's cute the first time you hear it, however after hearing it at least 10 times an hour, not so cute, I mostly try to tune it out.
The other things that annoy me are if they get into your space, believe me I have NO tolerance for that, or, if they are inconsiderate in blocking you in some way. I have learned over the years to say something, not put up with it, you have the same rights as they do and if you are getting stepped on, you HAVE to say something.
On to the positives, I have a TON of friends at the Market, I've known many of them for years. I have a friend at the Martinez Market "cookie monster" (can you guess what he sells?). I have so much fun at that Market anyhow, but having a friend there really adds to the experience.
In Concord recently there was this sort of creepy person there, you do get that now and then, and the thing is that it's nice to know your friends are watching out for you and have your back.
All in all I would have to say I have some pretty great Market neighbors.....ish :-)