Mistake 3: Not respecting their need to review products honestly
Since 2009, the FTC has mandated that bloggers who receive compensation for their opinions must disclose that financial relationship. In other words, if a blog post is sponsored, you have to say so. Nowadays, enforcement of this regulation isn't really necessary. The blogging community self regulates. Readers expect honest, expert opinions. Bloggers walk a fine line between effectively monetizing their content with advertising while being careful not to betray their core messages.
All of this just means that bloggers are going to give you their honest opinions. They really have no other choice. So don't ask them to lie. It's rude. Plus, you approached them in the first place because of the credibility that they have built with their audiences. It's important that they maintain this credibility.
Extra embarrassing: Following up with a blogger to tell him how much you disliked the review -- because your complaint is probably going to end up on the blog.