I've been in marketing for 20 years and personal branding is about credibility. Watching web 2.0 up close and Robert Scoble in particular is not something you want to emulate. Why? Lets take Robert as an example. He is a publicity hound and has been discounted by the true influentials in the business. He uses Friendfeed to portray an alternative picture of what is really going on. No one in the business really come to his defense or support him. Why? He doesn't help people. In fact he's traded off other people and their efforts only to promote his own. Conversely, successful people who have strong personal brands help people not promote their own advances.

Success is connecting with people and adding value.
Failure is stealing and self promoting.

How can you tell? Who is who? Look at endorsements? Robert has none. The only people who work with Robert are people who want to get publicity for their own agendas.

I think a big thing, especially for those of us who are "newcomers" to the industry, is to get involved and ask questions. Don't be afraid to approach people who are experienced in the industry; worst case scenario: they don't respond, best case scenario: you learn extremely valuable information. I've found that almost always, people value enthusiasm and effort; they may not spend an hour talking to you, but they will generally give you the time of day and potentially provide key connections to help you further your brand!