[GoblinLoveChild]

Im of two minds.

If i set up an event its usually to do with a plot ive been brewing for a while.. (this is mainly because my time is limited)
therefore there will be a few characters that have key information for said plot and i leave it to those who have staked most on doing the legwork building up to the event to chose who will come with them.

The other events I run are small quick little encounters to drop plot hooks and feed information on larger plots into the player base.
These events I dont really care who shows up because The whole point of the event is to -distribute- plot information to a wider audience.

In any such cases its the players choice to decide if they attend or not and how they behave, I will simply reward them accordingly with alignment shifts, npc reactions and faction reactions.  I am not above asking a player the reasoning behind why they chose to hang out with thier enemy, as a dm its easy enough to ask first.

As a team I can definitely say nearly every event run is open to any and all. The DM team attempts to always be inclusive as a general mandate.  Just be fair warned that if you go along with something in character that goes against your moral code or your evil overlords wishes, you -should- expect consequences