I understand what you are saying ston3y, but disagree. In my opinion, as Miriam commented on, there is no difference between a paid text link ad and a paid blog review. In the past google wasn't very good at identifying paid text link ads. Now they are very good, and the trust/authority doesn't pass. Just as some visitors to a site might not mind and actually get some value from paid text link ads, others have a different opinion and Google has addressed more than before thru their algorithm. While this may not be the case now, I believe with time the overall trust/authority will be deminished because of the muddy waters with paid blogs (as is the case now with paid text link ads). So its not something I would consider 'long term' even if does work for now.
A couple points to consider -
1) Does anyone think these blog posts are not being purchased for the paid links and search engine rankings as a motivation? If this is not the case, then check how many place the nofollow tag and I think you will be clear that there is considerable link motivation involved based on payment. We'd be silly not to think so since Patrick Gavin started ReviewMe and also text-link-ads.
Simple, read Google's stance about paid links. Google has been clear that they discourage paying for links to manipulate search rankings.
Lets be clear about the above, as many don't fully understand what is going on.
2) Lets say the value of a page is determined by how many others link to it. Not a real stretch, eh? Based on my experiences, if I put up a complete site of paid links it is very unlikely others will link to it. If I put up a complete site of non paid links the likelihood of others linking to it increases. Now taking this scenario to paid blog posts, if I post a paid blog review .... it is not likely that others are going to link to it. If I post a non paid blog post ... it is more likely that others are going to link to it. Clearly to me, even if some don't mind, in reality a paid post is not the same as a post just as a paid link is not the same as a link obtained naturally. Whether for search or humans.
Paid = Paid ... that's not muddy
The best links/blog posts are not paid (see mattcutts comment below) ... that's not muddy
Here was one of Matt Cutts
response when it was paid text link ads -
Reputable sites that sell links won’t have their search engine rankings or PageRank penalized–a search for [daily cal] would still return dailycal.org. However, link-selling sites can lose their ability to give reputation (e.g. PageRank and anchortext).
I would still consider the same to apply whether it is under the cloak of a blog review or any other type of 'paid' link.
Using your scenario as an example Ston3y -
I don't think its much different than a DJ being paid to do a commercial on the air.
... and I realize most others have expressed the same. Let me ask you this. If you were recommending a DJ, would it be based on his paid commercial spots or his non commercial influenced work. There is a difference, how humans act ... and search engines, based on my experiences.
Is there anyone here who would prefer to pay for an Adwords listing versus a free natural listing for a keyword. How about a paid text link ad versus natural link? How about a paid blog post versus natural blog post? Of course, everyone thinks the non paid listing is better, right? Paid = Paid.