I go to school at Boston University and took an Energy class with a Nobel Laureate in physics, Sheldon Glashow, last semester. He spoke in great depth about Thorium reactors, and is very supportive of the technology.

One of the main hurdles is that we have poured money into our modern-day reactors, and have constructed hundreds of plants. If we were to switch to thorium, we would have to essentially start from scratch - new research, new plant designs, new training, etc. It is very difficult to justify a complete switch from uranium, as it would be incredibly costly.

In other countries, however, thorium reactors could be very beneficial. Countries using thorium would not be able to produce nuclear weapons, which would give the world great peace of mind. This could minimize risks in unstable countries - we wouldn't worry if Iran was building a thorium reactor, for example.

There are also other types of reactor designs that use nuclear waste to create power. I believe our nuclear future lies with these types of reactors, rather than with uranium or thorium.