Although we know it can be a touchy issue -- informing the public once about a product (such as a press release might do) should suffice, however a constant barrage of the same information day-in/day-out could be the casting vote as to whether a blogger is overdoing it.
How does that affect you? When the search engines are putting an emphasis on blogs and RSS news feeds, the spam bloggers and take precious time away from the legitimate blogs. And the number of these spam-based blogs took a big hit in the last month. We refer you to the web site we looked at, Sifry's Alerts that can give you an idea of the big jump that has occurred.