It looks like when properly sized and placed, they wouldn't need any pinning. And while they do look goofy out there, they don't detract from the scenery any more than a houseboat, or tent, or canopy or anything else you see along the shore while enjoying the lake.Laketime, who manages my houseboat, offers these bags as an option, but you take them along with you on the boat, and they do not mention drilling holes to keep them in place.
These look like a great, low impact way of allowing many more boaters to enjoy the lake without being stacked on top of each other (more camp spots). It is a public resource and ALL should be welcome to use it, while following the laws, and trying to be decent human beings.