http://news.ycombinator.com/item?id=2723675 http://news.ycombinator.com/item?id=1009869
I think the first article was in reaction to the Fukushima disaster. It's hard to imagine this technology will actually make it to cars, whether it's safe or not, because of the r-word. Intriguing stuff, though.
The problem is that in this project, they are not using a thorium reactor. It is not a nuclear fission reactor of any kind!
They heat thorium with a laser or they produce a laser with thorium, or something like that, it changes from article to article. But the thorium doesn’t participate in any nuclear reaction. The energy involved in any nuclear reactions is so high that, with the current technology, it is impossible to produce a nuclear reaction with a laser (and perhaps it will never be possible).
Another important point is that they don’t have a working prototype, and the explanations about how it works are very confusing.
Some previous submissions about the same project: http://news.ycombinator.com/item?id=2877063 (14 comments) and http://news.ycombinator.com/item?id=2879219 (5 comments).
But your link is about a fusion nuclear reaction, that need a lot of heat to happen. And thorium is used in fission that are not temperature dependant.