Security researchers work together and share information in many ways and in many contexts that aren't constrained by company boundaries, but it's unusual for security researchers working for different vendors to join forces in a company blog.
However, John Leyden of The Register contacted us both when he was writing an article
on the controversy following Kaspersky Lab's dramatic demonstration of the way in which false positives can cascade from one vendor to another. This is a major issue, because it can and does introduce a serious bias into comparative detection testing and analysis. After responding to John's questions, we continued the discussion subsequently by email and found that we (along with most of the AV industry) were in agreement on all major points, and decided that it was more important to clarify those points, than to continue debating the detail of the demonstration.