I agree with Ian. To a point. Unions of private sector employees should be permitted to bargain and negotiate all what they want with management. But if they strike, call in sick, or damage property they should be subject to immediate firing and management should get to immediately hire permanent replacements. If the union is right and management will not be able to hire someone who is cheaper, more productive, etc. management will soon learn its lesson and either go out of business or rehire union workers. But if the union is wrong and management can hire better, cheaper, faster nonunion help, why shouldn't it be allowed to do so if the union has gone on strike and quit working?
Everyone needs to realize that you are only worth what it costs to replace you.
Re: public sector unions, everything that I have read indicates that public unions receive unrealistic benefits, so some reasonable and affordable cap on the same appears necessary.
Part of my "Ianistic" attitude towards unions is that I have found much of management, especially public management, to be as incompetent, bueracratic, and corrupt as unions.
And if a teacher goes on strike during the school year he/she should immediately lose their license to teach and should have their names placed on a child abuse registry..