OK ... here's a summary:
In fact, this distinction has been acted upon. According to dronejournalism.org, as of February 2014, the FAA had sent 17 cease and desist letters to drone operators in the United States since 2012. While most of those operators were in fact offering services for hire, as recently as March 2015, the FAA went a step further and sent a cease and desist letter to a hobbyist, Jayson Hanes, who uploaded video footage on YouTube that he had captured on his drone. The FAA figured that, while Jayson was not necessarily engaging in direct commercial activities, the fact that YouTube allows monetization of video uploads commercialized his video. Jayson maintained that he did not receive any money from Google, YouTube or any other party. The complaint to the FAA about Jayson came from a third party. The FAA often learns of drone video footage through third parties such as media websites or individuals who contact the agency directly.
It sounds draconian, but luckily the FAA wisened up quickly. While not citing Jayson’s or any other particular instance, the FAA issued a directive in April 2015 titled “Aviation-Related Videos or Other Electronic Media on the Internet,” where it noted that due to an “escalating number of videos or other electronic media posted to the Internet which depict aviation-related activities… the FAA must have acceptable evidence in support of all alleged facts in order to take legal enforcement action.” The directive reminded inspectors that media posted on the Internet is only “one form of evidence,” generally “not sufficient” on its own and most importantly, that inspectors themselves have “no authority to direct or suggest that electronic media posted on the Internet must be removed.” This is good news for you drone enthusiasts wanting to share your exciting, often breathtaking footage with the world.
Here's the FAA paper:
http://www.faa.gov/documentLibrary/media/Notice/N_8900.292.pdf
Here's the relevant quote from it:
Inspectors are reminded that:
• Electronic media posted on the Internet is only one form of evidence which may be used to support an enforcement action and it must be authenticated;
• Electronic media posted on the Internet is ordinarily not sufficient evidence alone to determine that an operation is not in compliance with 14 CFR; however, electronic media may serve as evidence of possible violations and may be retained for future enforcement action; and
• Inspectors have no authority to direct or suggest that electronic media posted on the Internet must be removed.
Note: Electronic media posted on a video Web site does not automatically constitute a commercial operation or commercial purpose, or other non-hobby or non-recreational use.
If you made a booming business out of drone videos on Youtube and it came to the attention of the FAA, they may view that as commercial flying but if you're only making pocket money with recreational videos that's something else altogether.