The many corporations use them yet shun from using them full time, open-sourced utilities and programs that are mostly free compared to their multi-million dollar software. Businesses are worried and they have the right to be for they have been used to very secure closed-systems that are designed to be used by them and solely by them. Open-sourced systems are on the other hand, mostly developed by a community of experts and users alike, with the occasional commercial backing or support from big names are wide open security risks due to their dynamic nature.
Like most open software, they need frequent updates to maintain proper operating status and most importantly stay secure to address security flaws that have been discovered after they were released. These companies were by no means totally bullet-proof in their security yet they had control over the mistakes that have more or less managed to stay kept under wraps due to their overall control of the environment within which they operate in. Opening their doors to software that frequently gets updates and revisions through the internet is quite a wide open door even with the security we have installed which is the major reason why bug businesses shun away from them.