Now, if I'll allow myself to wear the conspiracy hat for a moment I'd venture a theory that this reversal of philosophies between Canon and Nikon is arranged between the companies. A roughly equal number of people switching sides means people buying new lenses and accessories more than they would had they stayed put. A win-win situation.
I think you're onto something. Maybe it's a three-way conspiracy with ebay in on the action, too. Imagine all the money in seller's fees they stand to make