The gist of it is that any photos that you post on Instagram or videos on YouTube that were filmed in a National Park or National Forest are commercial in nature and are in violation of a policy requiring a permit for commercial photography.
Any such activity in a Wilderness Area is prohibited completely ... permits are not issued.
Obviously, this is not enforced--for the most part. But there are instances where the feds are in fact looking into situations where the policy is being abused. Typically it involves adventure athletes with sponsorships, or social media pages with large numbers of "followers". It has been especially active when images or videos are posted that show damage to park or forest land (as was the case just recently with the actress who carved a heart in the rock near Sedona.)
It will be interesting to see if new policies are enacted that address today's social media / sharing culture.
There are many possible variables on what qualifies as commercial.
But if you have a YouTube page and you receive any revenue from it, your videos from parks and forests require a permit, and your videos from Wilderness Areas are just plain illegal.

Interesting read:
http://www.outsideonline.com/1930546/wh ... eaking-law