Why is this redstone dust not powered?

The redstone lamp is powered, it seems, because it is lit. Then the cobblestone block in the middle should be powered as well with the same logic, but it seems it is not powered because the redstone dust upon it is not.

Why?

The third couple of blocks shows that a powered cobblestone block should power redstone dust that is lying upon it.

Solution 1:

I got an explanation in the #mincraft channel on freenode that redstone torches from the side only "soft powers" a block. Sufficient for a redstone lamp to be lit, but not to power redstone dust above it.

A redstone torch from below is on the other hand hard powering a block, also affecting the redstone dust.