Open source can save governments and enterprises tremendous amounts of money--but not always. Lower cost is not always the primary driver for IT deceptions. That's why policies of preference for open source, not mandates, make sense.

Open-source mandates have always seemed like a terrible idea to me, just as mandates to use proprietary software are. When a problem demands the turn of a screw, you don't want to be clobbering it with a hammer.
The Dutch police force understands this, which is why it has explicitly decided to prefer open source in IT purchasing, but to not use open source exclusively.
This is a sound, pragmatic approach to information technology, one that an increasing array of organizations are embracing.
Even so, sometimes our open-source aspirations fall short of reality. For example, the Symbian Foundation, the organization behind the open-source Symbian project, says it favors "open source wherever possible," yet it lists few open-source projects actually powering its IT infrastructure.
Perhaps its desire for software as a service trumped its interest in open-source software?
It's very possible. As stated above, cost, which generally favors open source, is not always the compelling differentiator.
Sometimes, however, cost weighs so heavily in open source's favor that a refusal to use open source demands an answer.
As reported on Slashdot, for example, the auditor-general of Canada's Ontario province issued a report indicating that the government wasted about a billion dollars on an electronic system for medical records when a credible open-source alternative existed, one that was already in use within the province.
A policy of preference for open-source software might well have averted such apparent waste of taxpayer dollars.
Preferences retain flexibility to fit the right tool for the job, while still encouraging open-source adoption. Mandates, like any form of coercion, tend to breed rebellion.
Just ask government IT employees throughout Latin America. During my last trip to Argentina and Brazil, I spoke with system integrators who specialize in open-source software. I asked them if their work with government organizations had become easier since those governments had passed legislation favoring open source.
Nope. In fact, the opposite seems to have occurred, as employees have dug in their heels to avoid being forced to deploy software that may be a mismatch for either their skills or the IT problems at hand. One comment I heard: "It's one thing to legislate and quite another to enforce."
Open source doesn't need mandates to succeed. It's growing explosively, and adoption is widespread. Preferences can help that, but mandates arguably won't.