There is a very interesting discussion going on over on the Guild Relations board yesterday morning while the servers are down - it spawned from a post that was a little off-topic for the forum itself, but turned into a very informational thread on the topic of Protecting your Guild's RaidID from Hijack.
What Is A RaidID?
At a Heroics and Raiding level, Instances in the game will "lock" your character to that instance for a period of time that spans from a day to a week, depending on the difficulty of the instance. The "lock" itself is saved as a RaidID that is viewable through your Raid communication tab.
What Does A RaidID Do?
Extremely simplified, it is designed to allow for the completion of difficult instances over a longer period of time (a day to a week) than normal instances, giving guilds and players a chance to take a break and go back at the tough bosses they're hung up on, later.
Its secondary function is to prevent players or groups from farming these difficult instances over and over in one day like can be done with the lower instances. Gear upgrades therefore take longer, and keep players and the guilds they join entertained for longer, hoping to make for a more stable social environment, I guess.
How Are RaidID's Shared? How Can They Be Hijacked?
A whole heck of a lot of ways.
Check out the forum thread linked above as there's some interesting discussion on the topic.
Another day I'll summarize all that great information and write up a follow-up post.