When did this become a serious conversation? 
I think this is a serious and important topic for photographers. Especially for those just starting out. I worked for free for a high end wedding photographer in the area for a good chunk of time. Heck, not just free. I paid tons of money for top of the line gear to provide him and his clients with usable images from high profile weddings. It turned out not to be free at all but rather a very inexpensive education from an established pro that had invested time and money in his education. I got more out of that relationship than he did by far.
The first wedding I did on my own I charged just $500. I was terrified but because they were getting such a great deal it took a lot of the pressure off. Later when I was charging up to $6,000 for weddings I would still find myself terrified but there was no relief from the pressure. Quite the opposite.
As a result of that time spent working for free I learned more about photography than I could imagine anyone could learn in school. It made me the shooter I am today and opened the door to the Microstock world and the world of concert photography for me.
In addition to the weddings I have shot charity events for free. I have shot high profile rock concerts for free, I have shot many events for my work and I think it's fair to say that each thing I did for free helped establish my reputation in Seattle as a photographer and landed me some incredibly high paying opportunities that wouldn't have happened if I was digging my heels in the dirt and holding to the principle that I won't take one picture for anyone for less than X amount of money. There are some events that need to be photographed but the coordinators simply don't have the budget. In my opinion there is no shame in helping where help is needed.
I would rather shoot free than hang out at home waiting for the phone to ring with a camera layered in dust and an unused shutter.
Mat