Al,
That doesn't look like the ones I saw at Wabamun and Mameo. They were not next to docks -- just out there offshore all by themselves, and there was enough superstructure so that they were easily visible even when there wasn't a boat on them. Otherwise, I would think they could be a navigational hazard.

Also, does your boat slide on and off the float either foreward or backward, rather than sideways? If so, with it alongside a dock that way, don't you have to keep the area clear for at least a boat length at one end in order to get it on and off?

At Sandusky Sailing Club in Ohio, the Thistle fleet had floating storage platforms attached to a main dock, but they were set up so the boat could be slid off and on perpendicular to the main dock, so a lot more boats could be accommodated.