Given the single-player nature they are emphasizing with an added MMO socialization aspect, I assume raids will be ALA Guild Wars, difficult sections of the game that are always there for YOU, but require you to invite others to join "your world" to best them.
"So if you go to Washington, it's buildings clean and nice. Bring a pack of matches...and we'll burn the White House twice!"
"Nobody's talking about extermination. No one ever does. They just do it." - Magneto
"Don't solicit for your sister, that's not nice, unless you get a good percentage of her price."