Twitter is a great example of personal branding. There are thousands of individuals with personal websites that feature their interests along with their career accomplishments.
I remember hearing a seminar a while back in which the speaker speculated that in the future we would all have our own personal website based on our personal name, perhaps even being assigned at birth. His dream was that this would be the way we would communicate with each other in the future.
Our personal brand is evolving daily, increasing in value as we continue to educate ourselves and gain experience. Part of adding value to that brand is marketing it to the world. What better way to do this than through our own blog, website, or networking medium.
Perhaps the future will feature employers searching the web for candidates instead of applicants searching for the right employer.