Interesting.
I don't know if it's illegal. On my blog last week I was paid to sponsor something about a website that supposedly listed reports for people who were ripped off. Anyone could submit to this report and the report had really high rankings. There are currenly lawsuits against the owner of the report because he didn't validate or verify the complaints before adding informtion into the report. Then...he charged large amounts of money to the companies who complained about being wrongfully listed on the report to have their information taken OFF the report. I don't know how the lawsuit will turn out.
So, in my opinion by all means you can review the company negatively. (
REVIEW STREAM: write review - get paid will pay for your review, btw and post it and index it online so you can tell your side of the story and it will be on the internet for the world to see) but I wouldn't go out of your way to damage their reputation incase you could be liable for it.