It's sad that they decided to go this route with the story arc. All Artie has to do is enlighten Data to the fact that he's
the great evil, and, bam, problem solved.
It would have been better, if slightly predictable, if Artie himself were the great evil, ala Dr. Jekyll and Mr. Hyde. I guess it could
still be that and Artie is just fuggin' nuts right now and the Data he was talking to was just a Fight Club
style projection of his own split personality, but they didn't even hint that that might be what's going on.
But it would certainly make more sense. How would Data have known about every artifact Artie collected, where they were stored, and how to gain access to them even with the plank of wood?