Arachnomancer is the sole creator of the list.
There are no sentinels, no sacred rite, no rhyme or reason to the names on the list.
She was the only person involved. In the final update to the list, and in this post, she reveals the true nature of The List.
That is proven. this is the first message of "The List" thread. The thread itself is much more amazing than anything you will find in my site. The depth of the paranoia, the extreme extent of the solutions created for completely random clues... all these things are the point The List makes.
Kudos to ara and everyone on the investigation team... except for one person. :D