Google does not like paid to blog posts. Matt Cutts, a Google engineer and head of their anti spam team, here clearly described why Google does not like paid to blog posts

http://www.mattcutts.com/blog/selling-links-that-pass-pagerank/

The posts just mentions that from a user’s perspective, paid blog posts are not useful. And with Google, if they think the post is not useful, then they will not give it top rankings.

And doing a lot of that can eventually affect your blog, as Google will think you’re blog is nothing but a paid-to-blog type of blog

I’d be very careful if I were you. You may not be affected now, but you’re threading on the gray zone area and sooner or later, Google penalties may kick in