[exelius]

I work with many big companies that use open source software, and the answer (as usual) is it depends.

If we're talking about a well-understood open source product like Apache -- probably not. Most companies will just have people on staff who understand those tools very, very well. Same goes for libraries (or really anything in the software dev toolchain). If the codebase is small enough for a single developer to understand reasonably quickly, there's no value in support.

But if we're talking something like a database server or operational software -- absolutely. You want an expert you can call who will help you fix your problem within a certain amount of time (SLA). Customers really only need support for production outages: assume your customers are at least as smart as you are, and given enough time they can figure their problem out. But they don't have time, which is why they want to be able to call you.