And all you have to do is browse /. and sourceforge to get a pretty clear idea, respectively, of how little that "community and goodwill" is actually worth. Hint: It won't make up for giving away the product of your labor.
Many companies who live by the "give away the razor, sell the blades" model would disagree with you. In addition, people hacking on a piece of software because they love it and demanding no pay in return is all the more value added to the product at no cost to the company.

As far as the service and support aspect being valuable: a source tarball is useless in and of itself. It requires time and effort to build a working, ready-to-rollout service from open source code.

Your company can either pay people to do that as well as in-house verification that everything compiled correctly, and maintenance for upgrades and all that, or pay for a support contract which will probably be far less than the number of full-time employees you'd need to maintain a program that you obtained "free-as-in-beer". In addition, with a support contract you have (ostensibly) knowledgeable experts to consult at any time, where without one you are depending on your programmers and admins having all the knowledge they need to quickly and reliably fix any problem they might run across.

The number of current successful companies is irrelevant to the question of whether free software can be capitalized upon or not. It's all about finding the right business model within a free software content that fits your particular product. So far, few have done so, but the numbers are growing, not declining.