Note: i know of MC-108. But this concerns the updating not the powering. But i have been unable to find something like this.

You can update a block whiteout touching it or (un)powering it.

When an block that can potential power another block gets placed or destroy or updated it may update other block within 2 block horizontally.

What I expected to happen was:
The block that i placed got placed and nothing else.

What actually happened was:
The block got pleased and it managed to update a block 3 blocks further in a sort of chain reaction. By updating redstone wire connection points and air and finally a piston. (no redstone power is not required)

Steps to Reproduce: (see image's)
I have labeled the images test_<test_nr>[Start/Result].

Test 1 update by placing a block 3 blocks further:
Step 1: create a setup like in test_1s.png.
Step 2: add the blocks as in test_1r.png.
Notice how some of the pistons extend without touching them. How ever this only happened when either a wire was connected or the wire was powered. Nothing happened when you connect something els to it.

Test 2 update by removing a block 3 blocks further:
Step 1: create a setup like in test_2s.png.
Step 2: remove the blocks as in test_2r.png.
Notice how some of the pistons extend without touching them. Similar to test 1.

Test 3 update by placing a block 2 blocks further
Step 1: create a setup like in test_3s.png.
Step 2: add the blocks as in test_3r.png.
Notice how one of the pistons extend without touching it. Only the placing of a torch has an effect.

Test 4 update by removing a block 4 blocks further
Step 1: create a setup like in test_4s.png.
Step 2: remove the blocks as in test_4r.png.
Notice how some of the pistons extend without touching them. It is also interesting to note that the pistons only responded to the repeater pointed to the piston. However if you remove the block under the repeater it does not mater whits way it was facing.

Test 5 update by placing a block 3 blocks further
Step 1: create a setup like in test_5s.png.
Step 2: add the blocks as in test_5r.png.
Redstone wire does not need to change visually for it to be capable of updating the piston.

Test 6 updating a piston by (un)powering a torch.
Step 1: create a setup like in test_6.png.
Step 2: flick the lever.
This manages to update and power the piston.