I have a suggestion for Mojang on this - create a one-way braking track. When a cart would enter the track block from one direction, it would slow the cart by a specific factor. When entered from the other direction, there would be no effect. This would allow the core algorithm to be maintained, give us 'cart-buffs' another tool to factor into our designs, and still have the penalty for moving too fast on a curve.
Just had the 14w26c load in for the first time and my torches have also disappeared. So far as I know, my saved world had no corrupted blocks
Further comment - it appears right now that every made item that was not in my character's possession is gone. Stairs, doors, walls, windows, chests, etc., are gone.
Unfortunately, I did not back-up my world first....
Going back to 14w26b brought some, but not all of my blocks.