In my previous work as a sys-admin I have worked for a number of companies that depend heavily on free software. If you use a commercially supported distribution such as Red Hat Enterprise Linux then you get high quality technical support (much higher than you expect from closed-source companies), but this still doesn’t provide as much as you might desire as it is reactive support (once you notice a problem you report it). Red Hat has a Technical Account Manager offering that provides a higher level of support and there is also a Professional Services organization that can provide customised versions of the software. But the TAM and GPS offerings are mostly aimed at the larger customers (they are quite expensive).
It seems to me that a viable option for companies with smaller budgets is to have an employee dedicated to enhancing free software and getting changes accepted upstream. For a company that has a team of 5+ sys-admins the cost of a developer dedicated to such software development tasks should be saved many times over by the greater productivity of the sys-admins and the greater reliability of the servers.
This is not to criticise commercial offerings such as Red Hat’s TAM and GPS services, a dedicated free software developer could work with the Red Hat TAM and GPS people thus allowing the company to get the most value for money from the Red Hat consultants.
If using a free distribution such as Debian the case for a dedicated liason with the free software community is even stronger, as there is no formal support organization that compares to the Red Hat support (there are a variety of small companies that provide commercial support, but I am not aware of a 24*7 help desk or anything similar). If you have someone employed full-time as a free software developer then they can provide most of your support. It would probably make sense for a company that has mission critical servers running Debian to employ a Debian developer, a large number of Debian developers already work as sys-admins and finding one who is looking for a new job should not be difficult. There are more companies that would benefit from having DDs as employees than there are DDs, this isn’t an obstacle to hiring them as most hiring managers don’t realise the technical issues involved.
This is not to say that a company which can’t hire a DD should use a different distribution, merely that their operations will not be as efficient as they might be.