Like others have said, the people are the only issue, they are generally the only thing you have no control over, everything else can be fixed. I've been to a site a couple of times where there is a team that is always there, now i generally don't come across teams but these guys seemed to act like they are "Elite" airsofters at a friendly skirmish sunday. So far i've seen different members:
Whine that the team they were on for the day was rubbish so sat out of the games for the rest of the day meaning the team had less people on their side and everyone had to switch up teams to make it even again.
Complain that someone shot them in the face when walking to the respawn whilst they walked through the middle of a firefight, rather than around the firefight.
One of them shooting people on their own team for not "pushing up" past the objective that was under their control because "We should keep\them in their respawn" rather than give them a chance to get back into the game.
The reason i have issue with this is, as much fun as it is to win, you've got to understand that everyone else there has paid money to enjoy a day out, berating people because your aggravated does nothing for you, your team or any new/first time players getting into airsoft. Also i'm not against teams entirely but you've got to pick and choose your times to be serious and that's what MilSim is for, but often see things around the internet of Teams going too far and thinking they're god's gift to airsoft.