Yeah, the biggest problem at the moment is hackers because it's so easy to do. My group runs their own server, so they're easily able to see who is hacking via the logs and ban them. You're also able to easily log out in combat, without alt f4ing. Then there's people that will log out, change servers, run to a spot behind you (if you're dumb enough to stay where you shot at them), log back in and kill you.
Not to mention the abundance of glitches in the game that allow you to dupe items easily and accidentally. There's constant reminders that the game is still an alpha.