The way I see it is if a company doesn't do a defensive registration on company+sucks.com, it falls under the 1st Amendment (many lawsuits, lost). Just tread easy, state facts with evidence, and you will be fine.
Coming from someone who wants Congress to look over ENCS/OMSG (military car sales to service members overseas).
To be honest, I've told the General Counsel to go back to law school, stating cases. Got an offer of $10,000 to shut mine down, but I won't -- I'm not a sellout; protecting my brothers and sisters of the Armed Forces. (Up and running since Feb 2012)
.sucks and .exposed aren't necessary, unless they have already claimed those names in dot com. In which case, it's your personal Yelp/gripe site. Just don't monetize it, and you will be fine.