So guys if your wondering some one came back with this great response that makes sense
Pistons (and dispensers and droppers) have a feature known as "quasi-connectivity" (aka "connectivity", "indirect power"), which basically says that pistons have the same activation shape as doors -- they can be activated by anything that would activate the space above them.
However, redstone components (torches, dust, etc.) only update other components within two neighbors (the spaces adjacent, and the spaces adjacent to those spaces). But updating the space above the piston won't update the piston (unless something else updates it).
When you turn on the top lever, that powers the block below it, which should activate the piston (because it activates the space above the piston). The redstone dust below the torch is two neighbors away from the piston, so when it changes state it updates the piston, the piston notices it should be activated (not from the dust, but from the fact that the space above it is activated by the powered block) and activates. The piston is receiving an update from the dust, but is being activated by the block diagonally above it.
In the variations you showed where there isn't any dust (or any other redstone component within two neighbors of the piston), the piston doesn't know that the space above it has been activated, so it won't activate until it gets updated by something. One way to update it is to place or remove a block next to the piston, which is the basis for many BUD circuits.
This is a weird unintuitive "feature" of pistons, but once you get used to it, it allows you to do many things you couldn't do without it (for example, it makes walls of pistons much easier). Many people consider it a bug, but Mojang has marked the bug report as "Works as Intended" … for now. Mojang employee Grum is exploring alternatives, but it's unlikely Mojang would simply remove this feature because that would break many builds that currently depend on it.
