It has long been my perception that NFA ownership was increasing. It wasn't until my early 20s that I really got into the whole gun culture, about the time I got my first job at a gun store; at the time, in the early '90s, I could count the people I knew who owned NFA weapons on both hands. Most of them owned full autos of one variety or another, although I knew one guy with a pistol-gripped short shotgun (as a smoothbore handgun, these are registered as an "Any Other Weapon", or AOW in gun nut lingo,) and the only person I knew with a suppressor had it attached to a MAC-10.
Now you can't swing a cat at a gun show without hitting someone selling suppressors, and I'm one of the few people I shoot with who doesn't own a can (or a short-barreled rifle or a full auto or a tax stamp of any kind.)
It looks like my perception is backed up by the numbers.
If suppressors keep getting more popular, I think one of the gun culture's next attacks should be to get them removed from the NFA. After all, they're good for your health!