Its only currency is photography. With very few exceptions, following the calling of photojournalism means living with financial insecurity. It means facing a constant struggle to buy a home, educate children, and plan for retirement. One prominent photojournalist compares it to being a poet, and there's a lot of validity in the simile. Society may value poetry, but it doesn't reward its creators.
Poets generally have to pursue other avenues to make ends meet.
For the documentary photographer commercial stock is one such avenue. It can make you a good living, one that can sustain you for years after the creation of the images. It can, without compromise, free you to follow your passion, and be the witness that society appears to need more rather than less. It certainly seems to me to be worth thinking about. Peter Howe is Director of Photography and Sourcing for Corbis.