Not only are people using YouTube as a medium to present themselves, many are using blogs as the new resume, presenting their skills in a way that is compelling and continually updated. Especially for technical professionals, resumes that provide a grocery list of skills doesn't tell the whole story. Blogs and other social media provide the opportunity to demonstrate those skills as well.
What's always interesting to me is how people appropriate technology for uses that were not originally foreseen. The social media resume is yet another great mashup - it pulls together YouTube, RSS feeds, social tagging (del.ic.ious, StumbleUpon), Twitter and Creative Commons all on a single page.