I learned something new today..
One of the main reasons why we fell in love with the 5D was the shallow depth of field and I have heard many times that a larger sensor creates a shallower depth of field which isn't technically true.
Depth of field is determined by the focal length and aperture settings of the lens and distance from subject. The sensor size only impacts the size of the frame. With larger frame you can get closer to your subject - where depth of field is more shallow, i.e. macro photography. With a smaller sensor camera you must stand further away from the subject where the depth of field widens. So in conclusion... a larger sensor size doesn't create shallower depth of field but is does facilitate it.
Also see this video.
