You can certainly toss the quilt in the dryer without a problem.
Laying the quilt flat to dry is a way of blocking it to the shape/measurements you want - squaring up the corner, adjusting a bit in the length for a straight edge, etc.
And, as you can see in this link, there are many, many opinions on the subject:
http://www.quiltingboard.com/t-102982-1.htm ;)
Sometime I block, sometimes I don't. And it has nothing to do with the batting. For most people, it's more an question of the "value" of the quilt to me, if it's going in a show to be judged, if they like that really flat look you get, or it needs a little nudge to be perfectly square.