I prefer to use peer reviewed journals of the highest integrity as the sources of what I would consider a good answer on this site. While perusing the JREF Forums, I was struck by a question asked there:
How did crackpot Electric Universe papers get published in a peer-reviewed journal?
The folks at JREF point out that "Bentham Open uses a pay-for-publication model." In this context, it means that the author pays the journal to be published beyond just basic administrative fees.
Open access has been criticized on quality grounds, as the desire to obtain publishing fees could cause the journal to relax the standard of peer review.
I can see this practice seriously impacting the peer-review process, as well as the impartiality of published papers (see my comment below as well). As of late, when trying to find papers, I am running into the Sage Journals a lot, and am noticing some papers there that make me ponder the impartiality and reputability of that site.
Are the Sage Journals truly a peer reviewed series of publications, or are they more of a vanity publishing?