I like the questions someone recently posted on the Faithful Discreet Slave:
http://www.jehovahs-witness.com/10/84199/1382759/post.ashx#1382759
How did the men who ran the Watchtower Society in 1919 find out that Christ had made this appointment? Did Christ tell the men who ran the Society in 1919 that he had done so, while appearing to them in a dream or vision? Did he send an angel to deliver this news to them? If he did not, how did they find out that Christ had appointed them to be his "Faithful and Discreet Slave" and thereafter act as his sole channel for distributing Bible truth on the earth? If Christ did not actually tell them, in some unmistakable way, that he had made such an appointment, then how has anyone ever really known that Christ actually ever really did such a thing?
It can be proven that Christ didn't tell them because they didn't even teach that they were the Faithful, Discreet Slave until well after 1919 (they still thought it was Russell)! Check out the whole post.