It's not at all clear that advertising on a blog will increase sales just because blogs are influential in the buying process. If I read a blog post that is an honest, unbiased review of a product it will likely contribute greatly to a decision to buy that product. But the power of the blog's suggestion had little to do with the fact that it was a blog and a lot to do with the fact that they were not paid to review.
If I'm reviewing simply to advertise then I lose a great deal of credibility and influence as far as the consumer is concerned. Advertising on blogs will simply shift them from the blog category to the retail or brand site category which may cost them influence.
Agreed. Furthermore, from personal experience I have clicked on adverts on search engines a number of times, but I don't remember ever clicking on a link on a blog post.
On a side note, where are you finding reviews that are "honest and unbiased"? I find them them pretty rare
If I'm reviewing simply to advertise then I lose a great deal of credibility and influence as far as the consumer is concerned. Advertising on blogs will simply shift them from the blog category to the retail or brand site category which may cost them influence.