By Yuki Noguchi and Sara Kehaulani GooWashington Post Staff WritersTuesday, October 31, 2006Media companies are of two minds about Internet video-sharing site YouTube, which rocketed to fame by letting users share homemade videos along with copyrighted clips from movies, TV shows and music videos.They are unsure of whether YouTube is a friend or a foe -- a threat that could siphon off their TV aud