A guy that I have played with several times is starting a raid guild and offered me an invite. Of course I explained that I am the leader of my own guild, but I offered my services if he ever needs a mage for one of his groups. He said his raid groups would be closed to nonmembers, even though he apparently trusts me. That put me off a bit. He is probably just giving me incentive to join his guild, but still... I personally have no problem playing with nonmembers that I trust, like Succubi before she decided to join us.