The reason nobody has run high-speed rails at over 300 km/h commercially (despite the ability to test-drive the trains to 400-450 km/h) is not only the ability for the train to run fast, but the wear and tear it does on the train tracks, the wheels, the suspensions, the joints, etc. You get the idea, and I'm only talking about hardware here. On the software side (which is the primary reason that caused the Wenzhou accident), the sensors, the signals, the anti-collision systems, etc. it's complication exponentially grows here.

This is why the world was very surprised when China claims to breakthrough (that no one else, with decades of high-speed experience, was able to) and run trains at 350 km/h commercially.

I truly believed China is using Wenzhou accident as a wake-up call to really check not just their trains (although also one particular model so far), but more importantly their tracks and software. The primary reasons for speed reduction, again, is not that those trains can't run fast, but is it safe to run that fast.

Personally, as high-speed enthusiast, I am personally upset by this. I was really looking forward to the real super train, China's much hyped 380 km/h model that it plans to roll out by 2014. But now, I have to settle at 300 km/h and 200 km/h (D-car).... yuck!