And indeed the Canadians have already thought of it. David Doorey's Workplace Blog- to which there is a link in the side bar-reports that "The Conservative government in Alberta has followed the Ontario lead by publishing Bad Employers on a government website." These sites only list the worst employers- those who have been prosecuted for labour law violations and have refused to pay resulting fines. The lists also appear to cover only government prosecutions, not for example enforcement actions for unpaid damages (such as unpaid damages in personal grievance cases).
However a start has to be made somewhere and the Department of Labour might consider this a useful addition to the web information it provides!