Why not??? It's already done in South Australia and San Fransisco, among other places I'm sure.
Surrey Mayor Dianne Watts said on the news tonight that she thinks that banning bags alone is not the answer, and that there should be a more comprehensive strategy in place to ban other things as well (Styrofoam, etc.). Obviously I don't know as much about this issue as she does, but it seems to me that banning just bags now and other things later is better for the environment than waiting to ban anything.
My guess is it's a cost issue? (Or is my ignorance showing?) I guess only time will tell.