TGV vs. ICE
Michael Jennings shows how a combination of Franco German rivalry and "Not Invented Here" syndrome means that despite the existence of high speed rail lines running all the way from Paris to Frankfurt, there won't be a direct high speed train linking the two cities any time soon.
The main reason is that the new Cologne to Frankfurt line has been built with such ferocious gradients (4% or 1 in 25!) that only the latest generation of trains, the ICE3, can cope with them. And these German built trains cannot run on the French LGV routes because the signalling systems are incompatible!
Still, at least the French and the Germans have got a high speed rail network!
Update: On Transport Blog, Patrick Crozier compares this with the standardisation of gauges in Victorian Britain under a privately run system. But I'm sure I remember reading that the 'gauge wars' in Britain were only ended by an Act of Parliament setting 4'8½" as the standard gauge. Pity, because Brunel's 7' gauge was technically superior in many ways. A bit like Betamax, really.