You can now sell links on individual blog posts http://www.blogged-out.com/2007/04/10/text-link-ads-announce-post-level-text-ads/ What do you think Google will have to say about this?
I can see why people would want to buy these but from a Google point of view it can't be healthy. Is it very easy to automatically spot TLA ads.
If you compare a typical link out in a blog post to one in a newspaper article how are they any different? Unless Google can track the link comes from a paid system how is to know no money changed hands and it's not in fact just a good vote ?