I can legally scowl at my neighbors every time I see them. I can spit on their sidewalk. I can do all kinds of things to be a bad neighbor, and it's all legal.

Likewise, simply putting a GPL license on your open source software doesn't mean that the people using it are going to contribute back, as you mentioned.

But what so many people fail to recognize is that the true power of OSS isn't about the software at all; it's about the ability to bring so many incredible minds to bear on a problem. That has nothing to do with license, and everything to do with culture. In some ways, the GPL actually stifles that culture, because it tends to attract people who feel no one should be allowed to make money from the efforts of the community, while BSD'd projects tend to be more more supportive and understanding of companies that turn their work into a commercial product.

By the way, in my (biased) opinion, I think a great example of how "Open Community" should work is how EnterpriseDB has been working with the PostgreSQL community on features for the upcoming 8.3 release. There's a number of very complicated features being added that are certainly better because of the collaboration than they would have been had either the community or EnterpriseDB gone it alone.