PR is not mentioned by John Batelle in a recent piece, 7th November, regarding the difference and importance between search and brand advertising but it is clearly at the party. Interesting analysis he has carried out on a fairly standard search enquiry on Google and seeing what is happening to a particular brand, in terms of which search enquiries can be termed demand creation (brand) or demand fulfillment (search). He says "In short, there are a lot of conversations out there that marketers can't "control", but that are vital to the brand's perception, consideration, and performance." These come from forums, blogs etc, very much areas of the conversational mix which would come under PR's responsibility.
The Economist this week also has a piece about marketing and online conversations.