The legality of anime on youtube is sketchy at best. But generally speaking, the posters have no legal right whatsoever to the material they post and are going 100% against the wishes of the legitimate copyright holders. That's why so many youtube users are suspended for their anime videos.
I doubt you'll ever see them here.
Currently, the only LEGAL places to download anime are on their creators' or liscence-holder's websites and through paid download services like unbox, itunes and bandaitv.