In MediaPost today, Chas (our VP sales/dev) writes:

Successful marketing on Weblogs today--and on traditional sites as they begin to imitate the participatory nature of blogs--means a different kind of engagement. It requires that the conversation begin at the first point of contact between the brand and the consumer.

Inviting consumer participation is the stock-in-trade of Weblog authors, and it's what has driven the enormous popularity of the top Weblog sites.