(v.) the act of illegally downloading copyrighted digital content and re-uploading it to the internet without the consent of the copyright owner.
While similar to file sharing, a ripload is often uploaded for online consumption, rather than download; sometimes under the pretense of appearing as the original creator.
Why would someone ripload to Youtube? Just link to the original, it's easier (and more legal) than using KeepVid or some SWF decompiler and then re-uploading it to their own account.
What's really surprising about Youtube is the amount of riploaded movie and television clips running ads. Who's approving these obvious riploads?