In his post he said he had trouble finding venues that would work with him on this. I know last time through Arizona he played Comerica Theatre (capacity 5500) and on this tour he is playing the Celebrity Theatre (capacity 2650). I would guess that this specific venue change was due to Comerica Theatre not wanting to work with his exclusive ticketing.
I'll bet you that if you look closely enough you'll find the Comerica (and most other equally large venues) is owned by Livenation/Ticket Master and as such will only deal with acts who work though Ticketmaster. That's the hardest problem to solve with ticketing, the fact that most venues of a decent size won't touch you unless you also use their ticketing service.
