[Sookei]

It is art theft. You cannot improve on your own work unless you do it yourself. Take for instant if you are tracing someone else's work and they have made a mistake and since you've only been tracing you don't see that mistake. That person is only hindering their self and basically learning a mistake from tracing. :P Kind of lame to trace if you ask me when there is so many resources out there like tutorials to teach you how to draw.