The Digital Visualization Group at UNC-Charlotte does a nice job of capturing the technological needs of a Virtual Cities framework in their Virtual Geographic Information System project. Of course, we need access to all that data that makes a virtual city possible. The virtual terrain project does a nice job of capturing the essence of what I've been seeing within the sciences the last eight years:
The impediments to data openness can be summarized by the human failings that cause them: Greed, Ignorance, Short-sightedness, and Fear.
Greed - Greed can be a issue, especially in countries where quasi-governmental groups operate without public accountability. Instead of treating geodata as a public resource, it is hoarded by organizations that exists as monopolies, bilking the public again and again for data that the public has already paid for.
Ignorance and Short-sightedness - Many governments are largely oblivious to the benefits of a publicly available geospatial infrastructure. They are often stuck in modes of thinking that are decades or centuries out of date, with no awareness of their own country's geospatial industry, or the myriad benefits of open geodata for education, planning, and countless potential future uses.
Fear - In many countries, the government allows mapping to be controlled by the military, which often treats every single bit of geodata as a potential secret that must be kept from that country's enemies - every road, building, and tree! Since 2001/9/11, this attitude has also crept into parts of the US government, with a handful of datasets pulled from the public in the name of "fighting terrorism", although most of these fears have since been shown to be baseless. The vast majority of geodata is useless to "terrorists", while being of immense value to the public.