I will not write for free. Period.
Some comments discussed that writers are the only profession asked to work for nothing, but I beg to differ. It happens a lot, especially in education. And not just the teachers. Support staff, "educational assistants" are expected to work earlier, stay later, cover classrooms, and babysit forgotten kids who sit forlornly on the couch because Mom's late or Dad forgot or day care wasn't informed of early dismissal.
While these public servants often work for less than we pay babysitters (except with taxes and dues deducted), they are often asked to "help out" in times of need. And they do. Dumb, dumb, dumb.
You're a professional. Whether your bagging groceries, engineering an oil rig not to explode, babysitting, writing screenplays, conducting brain surgery or monitoring recess, all honorable work deserves honorable pay. Get it. And don't work for free.
But the web creates all kind of iffy situations. I was linked to YouTube to hear Harlan Ellison rant about the disservice of working for free, and loved it, loved him. But I didn't pay a cent to hear it; not to him, YouTube or the LinkedIn referral (thank you Terri). I absolutely agree we should be paid to work, but I got all that for free. And you're getting all this for free. Get it? It's a brave new marketing world out there on the web, and we're all giving it away for free.