I get solicited frequently by open access journals. Anyone who has published an article in a mainstream journal will know that you almost instantly get hounded by email solicitations once your article goes live. They actually have "overseas" publishing houses that solicit you to write book chapters that seem legitimate, and sometimes they'll even offer you the role of managing editor, which is pretty appealing if you fancy yourself a scholar. I've had these offers and I was, understandably, a little skeptical. After doing some research, I found forums where other professional scholars had the same solicitations. Some bought into it, others didn't. Typically, these ventures are not necessarily "scams" per se. You can get a good editor and good contributors, but the intent of the publishing house is not to promote good science, it's to make money, so their gameplan is to let the scientists work it out among themselves and derive a profit from that. Sometimes it works, most of the time it doesn't because of poor quality control, which goes without saying.
That said, legitimate open access journals such as PLOS, etc., I believe are adequately peer reviewed but they charge a huge sum to publish, which is anathema to me personally. I would never pay a dime to have my work published. Every article I write takes months of painstaking research and effort of re-writes. I don't get paid a single dime for all those hours of effort. Nor do I get a dime when I referee articles. I am happy to pay for reprints of my articles and volume issues, though. I think that's only fair.