I wonder if Canon is taking a page out of Nikon's book and fixing prices across the authorized retailers. I hope it's just coincidence, but it seems fishy.
Canon routinely sets a minimum advertised price during its rebate periods. In order to participate in the rebate, retailers must set their prices in accordance with Canon's minimal pricing. As a result, the savings during a rebate period is seldom as much as the rebate amount. During non-rebate periods, retailers often discount the products to a "street price" that is below Canon's MSRP.
What was unusual is that during the pre-Christmas rebates, retailers seemed to have a little more flexibility. (For example, posting an advertised price and then granting a discounted price if you added the item to your shopping cart.) I don't know why that was, but Canon was obviously trying to boost sales before the end of the year and I suspect they were willing to give the retailers a bit more leeway in order to meet their sales goals. (Plus, of course, most of the rebates were bigger than the ones we are seeing now.)
Finally, on almost all products the two major retailers, Adorama and B&H watch each other very closely. If one offers a special, the other usually quickly follows suit. Since they are the big guns in the U.S. most other mail order retailers tend to follow suit. A few will try to undercut the big two by a few dollars. I've always bought from Adorama or B&H and never wanted to risk trying someone new, although I'm sure some are reputable.
