What people don't realize is that everything uploaded to YouTube, the uploader has agreed to give certain rights to YouTube and any company that might buy them out in the future...certain rights...among them to reproduce, distribute, make derivative works from your content, and profit from it... without ever compensating you for it.
That means, for example, that a small time independent band can make a music video and upload it...and YouTube can take the music out of it and sell the rights to use it to some company and the band's song could end up being used in a commercial for hemorrhoid cream.
YouTube, or any company that buys YouTube (in this case, Google) would be the sole entity to profit from this. The band would become famous for their one-hit advertising wonder...but never receive a dime for it.
Or even worse if something like this were to happen:
An artist creates and uploads a short animation featuring a really cute bird with a coin. YouTube sublicenses derivative works based on it to Disney, which makes a full length feature movie based on the bird character and makes billions on it. Then they make even more off the merchandising, the tv series, dvd's, etc. The bird becomes as well known as Donald Duck.
YouTube gets their cut. The original artist gets nothing, except maybe a mention in the credits, if he is lucky.
Is it fair? no
Is it legal? Yes, because they AGREED to it when they uploaded the video. Their agreement says "exploit me" all over it.
Be really careful when you agree to things...make sure you know what you are getting yourself into.
For clarity, you retain all of your ownership rights in your User Submissions. However, by submitting the User Submissions to YouTube, you hereby grant YouTube a worldwide, non-exclusive, royalty-free, sublicenseable and transferable license to use, reproduce, distribute, prepare derivative works of, display, and perform the User Submissions in connection with the YouTube Website and YouTube's (and its successor's) business, including without limitation for promoting and redistributing part or all of the YouTube Website (and derivative works thereof) in any media formats and through any media channels.