The post below was motivated by the minimum wage debate. I find it a little mysterious that people favour the minimum wage over cash top-ups funded from general taxation. Maybe it's just about the principle and not about the consequences.
I don't believe that a minimum wage is effective in helping the poor, but I would oppose it even if I did on the grounds of freedom. Maybe those in favour of the minimum wage are also more concerned about the principle; the need to make a statement about what workers deserve regardless of the consequences for the poor. Of course we would never actually say this, but I'm sure it must be something along these lines.