At 2NMC, you heard Dave and I talk about the importance of leaving comments on blogs so that your audience can triangulate you -- associate you with events, people and issues that impact your music. The side benefit has been that the links back to your own site also elevate your position in Google. That's going away with the addition of this new "nofollow" spec, because robot spammers have abused the feature so much, but I'll still encourage all of my clients to remain active on blog comment logs. They're still a great way to introduce yourself to interested human audience members.