If you aren't careful with the music you use in your facebook videos, youtube videos, and even podcasts...You might end up paying money to people who run ads and make money ON YOUR VIDEOS!
Thanks to fine print and content id networks it's near impossible to find music that is actually royalty free. This is why I personally compose and record music specifically for your commercial projects. It's a one time fee and you never pay a cent to ad networks when you use it.