One little point that all too few seem to appreciate. In Gordon Brown's speech on how we're going to make ourselves poorer reduce carbon emissions he let drop this little comment [3] :

There would be "hard choices and tough decisions" but he said a new low carbon economy could bring thousands of jobs.

That's how we know that it's going to make us poorer of course. Now it still might be a wise idea, might not be as well, but my point is rather that everyone seems to insist that "creating jobs" via such schemes is a good idea. It isn't. It is most certainly not a benefit of such schemes, it is a cost. 

For of course if all those busy little workers were not installing tofu machines to light the yurt growing communes, they'd be off doing something else, curing AIDS, planting turnips or hanging politicians, all things which would arguably increase human happiness more. We are therefore poorer by those things which they will not be doing.

This is a blog post, so I'm not going to try and work out whether what they're going to do in their new green jobs increases human happiness more or less than the alternatives they would do without the government intervention: I just want to insist that we should regard this creation of jobs as something to put on the costs side of our analysis, not the benefits.