Why does it have to be designated campsites to the exclusion of choosing your own site?  I believe the popular and most used campsites will remain popular and used, designated or not.  Many often used sites would likely benefit from having a latrine and a specific fire ring location.  Other sites, such as islands too small, could be posted that they should not be camped on.  The vast majority of campers would see the logic in not using the over used sites and other campers might need the gentle guidance a posted sign would present.  At the same time why not allow campsite choice as well for those travelling less popular routes or lakes or instances when there are too many canoe parties for the number of available sites and for solo paddlers who generally require very little space for an overnight stay.  :-?