World Map Shows Countries Requiring Open Source Software (networkworld.com)
"Europe and South America are the biggest hotspots for open-source use in government," reports Network World, while Bulgaria requires all software written for the government to be FOSS. Slashdot reader alphadogg quotes their report: It's become increasingly common over the past decade or so to see laws being passed to either mandate the use of open-source software or, at the very least, encourage people in government who make procurement decisions to do so. Here's a map of the status of open-source laws around the world.
Red Hat has grown almost 100% over the last five years and has billions in revenue. The counter-argument would be Microsoft, but you may have noticed Microsoft has been open-sourcing stuff too, and making billions.
At the same time, open source saved my last employer, a government agency, a ton of money. In many cases, it just works better all around to share. The company selling the software and services doesn't have the cost of developing everything from scratch, and customers aren't dependent on a single vendor.