The FDA is only part of the problem. Existing (and future) state tobacco/vaping laws may also effect many of us especially in states that already require face-2-face (no internet) tobacco purchases. U.S. customs and the USPS could become a major PITA, it is they not the FDA who would be responsible for policing shipments. However, I seriously doubt seizing vape gear will be priority anytime soon, likely not even a blip on their radar regardless of what the FDA desires. At least until/unless key members of congress makes it a priority but I really don't see that happening for years. I'll be ordering gear from overseas vendors the same as I do now until customs starts seizing the shipments.
Unlike some posting here, I don't think U.S. customs is a joke, undermanned or underfunded. Post 9/11 they became part of the department of Homeland Security, an agency with 240,000 employees, an undisclosed number of contract employees and a 40+ billion dollar annual operating budget. That's more funding than most of the world's nations spend on military/defense. IF they wanted to make our lives difficult, they certainly have the tech and resources to do so but I'm counting on their indifference, the same as the did with Canadian meds and internet pharmacies for so many years. Don't know if they still do but back in the late 80's if you had an illegal shipment seized by customs your name and address was "flagged" for 100% inspection on all future shipments. If that's still the case it could be a problem. Their tech, authority and budget has increased tenfold since then. Good news is the Chinese -are- masters at evading import restrictions through clever marketing descriptions of their products, they've been doing it for decades. Coupled with the low priority I expect vape gear will be assigned I think we'll be ok for quite some time.
All this speculation of widespread black/grey markets and illegal transactions is also interesting. Absolutely no doubt if the conditions are right many people will seek to profit from peddling overpriced, dubious quality, illegal stuff on the streets but consider this; We live in a country that has 151 million people in its workforce, 1.1 million of them are state/federal law enforcement. Many people don't think U.S. law enforcement is effective at stopping unlawful activities and in truth they really aren't. They are however extremely effective at arresting/charging people with criminal violations of the law and making those charges stick. Fact is the U.S. manages to arrest, convict and imprison 1 out of every 115 adult citizens and has the highest per capita rate of incarceration in the world -by leaps and bounds-. It helps feed the growing for-profit privatized prison system and also keeps the "army" of law enforcement personnel busy while at the same time justifying their existence/expense. The war on drugs didn't stop its availability on the streets but it has left in its wake millions of people who are now and shall forever be convicted felons. 1 out of 115, feeling lucky? Just food for thought.