At the Open Source Think Tank conference in Napa, one of the CIO attendees described "transparency" as a major value open source providers give him. His sense was that open source vendors are on his "team," not adversaries.
Every CIO knows that the software they are acquiring has bugs. The question is: how closely will the vendor work with me to resolve the bugs I find?
For proprietary software vendors, the incentive is to hide or minimize those bugs and pin the blame on some other vendor's product. If I am an open source software vendor, I know you have access to my source, so it does me no good to hide my warts.
The net result is that CIOs see a greater alignment of interests when they work with open source vendors.