Without even going to the site, it is clear they are using someone else's trademark in the domain name.
Having youtube in the url is trademark infringement, but also the site itself is illegal because it breaks YouTube's TOS of proper use. According to the terms, you may not rip or distribute YouTube videos off their site nor can you scrape YouTube. You're only allowed to use their API and the functions it provides (which doesn't include getting the flv or source of the video).