From Nature:
Beall told Nature that he stands by his decision and that he has received dozens of e-mails from the scientific community outlining bad practices at Frontiers.
Beall names some controversies that he says helped raise concerns about the Frontiers journals. These include a Frontiers in Psychology paper suggesting that conspiracy theorists do not believe in climate change and a Frontiers in Public Health paper raising questions about the link between HIV and AIDS. Both ignited Internet firestorms on publication. More.
Real concerns? Backlash against open access publishing? Floor’s open.
Re conspiracy theorists: It’s what they do believe in that—one would think—would be of more interest.