Recall this post from December, 2006? It was about how the Iranian government was actually rebuilding things in Afghanistan; things like electricity supply, fibre-optic interconnection, roads, and maybe even a railway. Not just that, but they were supplying today's version of Marlboros and jeans; the best Internet connection in town.
The Christian Science Monitor goes to Herat, (hat tip) where the other end of this activity is visible; a thriving private sector. Build the infrastructure and they will come. I'd love to see, by the way, any current figures for how much money, between DFID and the Army, has been a) committed to Afghan aid and b) spent. The figures in December were far from encouraging.