Many players have posted elaborate criteria for restriction. Wizards posted quite clearly what their criteria for restriction is. The objective criteria for restriction is tournament attendence. When tournament attendence drops, the DCI will restrict stuff to get attendece back up. If only restricting trinisphere is the best way to raise attendence, that makes trinisphere the correct card to restrict based on the criteria for restriction.
Except that wasn't the criteria that was cited by Aaron in either this article or the article where Trinisphere was actually restricted; there was no discussion of tournament attendance drops in Vintage events. While there are a number of Vintage events held, which WotC could have tapped into the numbers for, they are unsanctioned event; and has been suggested before, perhaps there is a taboo against using that kind of data without the "official" sanctioning. Regardless, Aaron's comments regarding Trinisphere was with regards to the lack of interactiveness and "unfun" nature of the card; there was no mention of tournament attendance.
Epeeguy is completely correct. Certainly attendance is a factor in banning and it probably is a factor in restrictions as well. But the critical fact is that wizards did NOT rely on attendance in deciding this particular restriction.
If anything, T1 tournaments hit their highest attendence with 3sphere legal: 200 people at waterbury, 136 in syracuse, etc. Record numbers.
Plus sanctioned tournaments don't count for piss for DCI t1 policy, and they know it.
