I've been a life member of the NAFC for quite a few years, they have a pretty decent magazine...but not much in the way of fly fishing. They have an online forum too, but it doesn't get much traffic compared to more focused (species, tackle, region) forums do.
I was a product tester for a little while, but never submitted a review of what they sent me because they sent me stuff I wouldn't use. They make it sound like you get great stuff to test and keep, and you do keep what they send ya. But when they send you 3~4 plastic baits to test that would probably work great for warm water fish, and you don't fish for them how do you give them an honest review?
Not everyone gets a new trolling motor, or canoe, or etc...probably have to work your way up the product testing ladder to get anything worthwhile.
Long story short, it's not a scam, just a way they use to grow their membership. I look forward to reading the magazine when the new issue comes out. This month actually had an article on attractor flies, it was good.