Should you write for free?
I am kidding, of course. There has been much talk about this in journalism circles as of late.
The answer, to me, is yes if assigned and for a publication.
If it's your own thing on your own site or blog, more power to you. Yes, you can benefit from traffic and you should consider the options if approached to republish.
But flip the argument for the publications (should you pay?) and the question is solved easier.
Because you get what you pay for.
Back to work, everyone.