The EU recently passed a new copyright law that potentially creates massive problems for private individuals uploading content to the internet. Copyrighted music in the background of your video can create a copyright violation take down situation.
https://en.wikipedia.org/wiki/Copyright_...
Sound effects are kind of weird in the copyright world. Some sound effects packages are copyrighted, some are not. I don't know the criteria for determining if a package or a specific sound effect is eligible for copyright. That would be a topic for a future blog post.
A really good source...