The move appears to target the "Let's Play" community, in particular. Let's Play series authors often produce full video walkthroughs of featured games, with voiced or subtitled commentary accompanying gameplay.
When a "Content ID Match" is claimed for a YouTube clip, the claimant is given the right to place an advertisement at the beginning or the end of the video. Content ID Matches differ from DMCA takedown notices or outright video removals, in that matched videos remain viewable by the public and do not count as a copyright strike against their producers. All revenue earned from views, however, will go to the content's copyright owner, rather than the video uploader. The act is common for publishers like Activision, Electronic Arts, and Square Enix, but it's only recently that Nintendo has joined in the practice.
Multiple affected authors have come forward on Reddit to confirm Nintendo's new policy. To date, Nintendo's Content ID Matching spree seems to focus on recent releases like Super Mario 3D Land, Luigi's Mansion: Dark Moon, and New Super Mario Bros. U. Currently, Let's Play videos for older Nintendo-published games are unaffected.
Nintendo explains its position in a statement issued to GameFront: "As part of our on-going push to ensure Nintendo content is shared across social media channels in an appropriate and safe way, we became a YouTube partner and as such in February 2013 we registered our copyright content in the YouTube database.
"For most fan videos this will not result in any changes, however, for those videos featuring Nintendo-owned content, such as images or audio of a certain length, adverts will now appear at the beginning, next to or at the end of the clips. We continually want our fans to enjoy sharing Nintendo content on YouTube, and that is why, unlike other entertainment companies, we have chosen not to block people using our intellectual property."