Doing commercial photography for free?

If I choose to do commercial photography for free, purely for the fun of it, am I committing a cardinal sin by totally undercutting the efforts of other photographers to make a good living by charging the highest prices possible?

In other words, in a money-value society, can a pure amateur coexist without moral concerns for diminishing the income of others? Am I bound... or should I be bound... by the moral values of others, to the effect that if your work has monetary value, then by selling it cheap you destroy the value of others' work, and so forth? Even worse, by photographing for free?

In a sense, in our capitalist society, am I my brother's keeper? If you take photos for a living, do I have a moral obligation not to do anything to harm you? Is this a discussion that should be posed in collectivist vs individualist terms... or in barbarian vs Christian terms, or what?

In the real world, it's not just Jon trying to set off an interesting discussion. It is more like the explosion of free internships, so many people working for free in corporate-land these days, and maybe in the near future, actual jobs where one will work for free, or for food and shelter and the glory of being part of some mega-corporate tribe.

But in the meantime, is there room for a pure amateur in the modern workspace?