I blog on Huffpo when the fit takes me. I blog on my work site and professional site. It has its various rewards. None of which has to do with getting paid as if I were a professional freelance writer.
Why people keep insisting that we should emulate the failed business model of professional freelance writing, and that if it fails something is wrong with the world, is beyond me. If you don't want to blog on Huffpo -- don't. I rarely bother, but I don't feel exploited when I do.
The truth is that Huffpo is one of a number of businesses that has figured out how to be a platform for something folks want to do. If it helps, think of Huffpo as renting soap boxes. The orators standing on them generally do not feel exploited.