Barack is LinkedIn
There are lots of examples of Web 2.0 having a big impact in the 2008 Presidential race. The latest I noticed today is Barack Obama asking a question on LinkedIn. He asks "How can the next president better help small business and entrepreneurs thrive?" In 10 hours he has more than 800 answers, including mine.
I think that this is a great strategy. I even figured out how I was linked to Barack through his LinkedIn profile. Getting to hear from people directly is a great research tool. I think that Barack also build support just be being 'out there' in cyberspace. I am sure he's got staffers who are doing this for him, but it's good PR.
I'd encourage you to interact with the campaigns through these mechanisms. I am not ready to decide who I am going to vote for based on their Facebook profile, but I think that some people will.