I would not take the chance. We have been members of Passport AMerica for many years now, and have been very happy with it. It is definitely a scam. While some may not have been happy, we have had VERY few disappointments in the campgrounds. We rarely stay in one campground while on the road for more than a few nights, and the Passport America campgrounds have been more than adequate for that.
You definitely have to read the directory carefully, because there are limits as to when the discounts apply. Obviously some don't apply in their busy seasons, but that is to be expected. We have generally used their campsites for 15 to 20 days/year, which means the membership costs us roughly $2.00/night. That seems like a good deal to us, and they now have over 1900 paricipating campgrounds in north America.
Ed Headington