Closed Source Software is opaque. If you have concerns about the software, perhaps that patents have been breached or intellectual property rights infringed, you have to take the supplier's word that all is okay.
Open Source Software is transparent. Because you have access to the source, you have the Freedom to audit the software (or employ a third party to audit it for you).
In these days of increased compliance issues like Sarbanes-Oxley, you have to be able to prove that you've done your utmost to ensure that your shareholders will not lose value should a software package bring problems to your business.
By using Open Source, and being less dependent on opaque proprietary software, you increase the transparency to your shareholders as to how you gather and store your company data.
