I'm no legal expert but in my opinion if you have a business name DroneVideos LLC and use it to shoot videos commercially, then yes, the FAA would more than likely go after you without a commercial license. If on the other hand you have a business CustomCreations LLC which primarily sells photographs and videos from a tent at an art fair or some small shop somewhere and some of those photos and videos happen to come from a drone while others come from ground based cameras then I'm guessing they would leave you alone. Just an assumption on my part but the rub is, who shot the pictures or videos from the drone and for what purpose? What was the intent when it was done? Was it leisure? Or was it, hey, I can use this footage for my photography business? If it was done in leisure and later you decided, hey that footage would really be good to have in my shop, etc. is where I think it gets really murky. If on the other hand your drone is just another piece of photographic equipment used by your business, then I would say, get a license. Either way, its a risk someone has to decide for themselves whether or not to take.
Here's another example, what if you use your drone for fun, you've shot a whole lot of photos and videos over the years. Years later, you decide to open up shop and try to sell what your media, is it legal to do so? Again, not very clear cut in my opinion.
If I'm using my drone for leisure/hobby, I'm still FAA registered, just not yet as a business nor was my drone procured and/or claimed as a business expense. I would like to eventually get my commercial license so at least I have legal options.