"A limitation of the study is that it did not use iPS cell lines that were created without viruses, said Jacob Hanna, a post-doctoral researcher in the laboratory of Rudolf Jaenisch at the Whitehead Institute for Biomedical Research in Cambridge."
I think the above statement taken from the article is an important one. The company involved is working on technology that would use iPS cell lines created without viruses, therefore, they are looking to find fault with iPS cell lines that are not created that way. Just my opinion, but that's how I read it.
