Six weeks now into my new role, and it is becoming clearer to me that there are still major challenges for the open source community in providing services into corporate environments.
Whilst the “products” from the open source community are often as good (if not better) than commercially licensed software, at the moment it seems that the integration layer is the challenge. By from Microsoft, IBM, SAP or Oracle, and partly what you get is some level of assurance that you will have products that co-exist fairly cheaply. With open source, you can end up with a heavy burden of bespoke integration, which ultimately cuts into any cost advantage of no licence fees, and also reduces opportunities to integrate in the future.
mmitII 
Whilst Open Source can be good if not better than paid for stuff it can be a real pain in the butt to manage. I have worked in an environment where open source did play a part but if any bugs were found we would have to spend hours trawling through forums to find fixes or we had to post the problem and wait for solutions. In the end we went for the paid for options as the support is excellent (usually) ;).
I cannot imagine a place where bespoke integration is at the heart of any company's IT infrastructure. Any company that is setup in such a way is best placed to ripping it up and starting again. How can Active Directory and other top services be expected to integrate with such a setup up. Simple Answer – THEY CANT!
Open Source can have its place, dont get me wrong, provided it's tested and integrates well but it should NEVER be at the heart of an IT infrastructure. It's the work of a Mad Professor that.