I still think that maybe it's going to be a person. Evan Marriott maybe?
Last night if they HAD gotten rid of Whitney I would have been more suspicious, but I'm willing to wait and see before I buy into the Canary C. Burns theories. If the firing seems to be random every week, then we will have our answer.
My own pet theory is that the person who is closest to catching on or has the least "buy in" to the concept of the show is the one who gets canned. Daniel already seemed to have an idea that something was up and Elli was definitely suspicious, last week I thought that they were both clueless though.
But I won't be surprised by a monkey with a magic 8 ball.