Don't forget that there is likely to be a legal issue in doing that. Formally posting something somewhere can leave oneself open to being sued (slander and/or libel) or getting a reputation for "slagging off" companies. There is a balance to made and I think that personal enquiries within ones own network is best.
You can damage your career or destroy your marriage or health with a poor job. Recruiters will lie or ignore conditions that don't affect them. A bad company that needs people due to attrition might be a recruiters bread and butter client.
There are thousands of companies, many with toxic or dead-end environments. Not every network knows about every company. Something as simple as a numerical score or comment whether the company would pass the "Joel Test" serves a decent substitute for true internal knowledge.
So far among the four user groups and other events we've talked about this at , the reviews that exist on Glass Door are running about 90% accurate. You can usually spot the crazies and bashers. And there's several local companies that have gained by having positive, but accurate reviews. And several confirmed companies with extreme technical debt and mismanagement.