there are a couple of great threads on here about how to do it. I believe with some SEO knowledge one could do it for themselves, with little to none you should read the how to's on here with the throught process of determining who you are going to hire.
So True! Thanks for the idea of negative seo on the article!
Why did you ask the same thing 2 years ago?
http://www.blackhatworld.com/blackhat-seo/black-hat-seo/316780-moving-bad-review-gov.html
If this is a new negative article then I would suggest you fix your business practice
If its the same, then the advice above should help
To those interested in this issue. I do RM for a living. There are a number ways to push negative reviews for example off the 1st page of the SERPS. And it does not have to be just positive reviews. Yes LinkedIn is one option. You can also use Web 2.0 properties like wordpress.com, Tumblr.com and Facebook (fan pages) as just a few examples.
You can PM for more info on this process.