So I decided to try and create an enderpearl dispenser. Long story short, I had troubles with the design. The design I then came up with, which SHOULD work by minecraft logic does not because of this apparent bug.

So I have 2 dispensers stacked on top of each other. Both dispensers are powered by a redstone signal running to a block next to the dispenser(top one has it beside it, bottom one has it underneath it). As minecraft logic goes, a block being powered by redstone will only provide power for the object next to it.

The way my design would work is the redstone is always powered(clock ticks to dispense the enderpearls). The bottom dispenser will only fire ONCE while the top dispenser is being powered. No matter how many times I power/unpower it. Once it fires that one time, it stops completely. Now I did get this to semi work in 1.4, except it dispenses twice. Once when it gets powered, once when it gets unpowered.

However, in 1.5, and 1.6 it acts the same as it does in 1.7. Which leads me to think it was either disabled from working since 1.5, or it has been a glitch since 1.5. The provided screenshot shows how I tested it in the different versions. The line of redstone you see on the right was to see if the top dispenser was outputting a signal at all, which it did not. The setup in the screenshot is a simpler version to get the point across, but still follows the same idea as my enderpearl dispenser design.