Open access publishing is great. Anything reducing the friction inherent to the spread of scientific results provides a benefit to society.
That being said, reading the list of PLOS ONE papers on Complementary and Alternative Medicine is disappointing. I like PLOS journals and I know how PLOS ONE works: papers have to be technically sound but any judgement beyond that is limited. The burden of proof does not lie with the journal. The problem is with studies clearly based on a shaky foundation. There's this recent work with using homeopathy to treat depression, for example.
There's an Ars Technica piece about that paper, though there appears to be some debate as to whether all of its author's claims are justified. The comments on the PLOS ONE page appear to have been deleted.* Even so, extraordinary claims (i.e., that homeopathic remedies have any therapeutic effect beyond placebo) require extraordinary evidence. If we are to assume that any study along these lines has been designed and performed properly, a positive result is essentially disproving everything we think we know about science. Researchers shouldn't handle homeopathy studies without that philosophy.
I'm genuinely worried about how much of the research into alternative treatments may, in fact, provide solid results and legitimately novel approaches. It's awfully difficult to find such results when they're diluted in a sea of studies with questionable premises.** Hopefully, public commentary will provide a helpful filter.
*The corresponding 404 page is cute and panic-inducing. Where did that sample go? How long has it been missing?
**That's a half-finished homeopathy joke, there.