Unauthorized use of YouTube Content ID
YouTube aims to promote original and creative work. Doesn't authorize the use of Content ID to insert your sound recordings gratuitously into popular 3rd party videos. The general principle is that you shouldn't be using other parties' popular videos to monetize your sound recordings and that the use of your music in videos should be organic user-generated content. If your sound recording is to generate a valid claim, it must be because it is an integral part of the video it appears in, and it was added organically.
Examples of unauthorized usage of YouTube Content ID:
1 Inserting your sound recording into a Simpsons episode. The viewers of the video came to watch a Simpsons episode — they did not watch the video to hear your song.
2 Creating a compilation video with famous musicians' songs and inserting your sound recording as an outro.
3 Overlaying your music on a scene from a popular movie.
4 Using misleading thumbnails and/or titles to get users (especially children) to click on your video.
Please note that this list is not exhaustive. It's just meant to provide a few examples.