There is a growing need for a tool that allows outsourcers to blacklist or at least publicly comment on unreliable translators. Each translation company has its own grading system but, generally, information is not shared. Dealing with unprofessional translators is costly, time consuming and can have serious reputation consequences for a translation company if and when corrective steps are not pursued.
It is fundamental that such tool is created through the cooperation between agencies and freelancers, for instance on a site like Proz, and I am convinced that professional translators would benefit from it.There are many things wrong with this, from the fact that such a system is morally repugnant (given, among other things, the power disparity between translators and agencies, as a wiser colleague points out in the same thread) to the certainty that it would be abused by unscrupulous agencies, and to the completely unwarranted facile assumption that "professional translators would benefit from it".
Even if one wanted to look at this from the point of view of a translation agency, such a system would signify a complete abdication of the translation agency's own responsibility: "dealing with unprofessional translators is costly, time consuming and can have serious reputation consequences for a translation company" - yes, selecting unsuitable translators would damage a translation company's reputation - and that's precisely why translation companies should take full personal responsibility for the whole selection process, without trying to fend off all or part of the selection to an unethical and unprofessional idea such as this.