As always, I prepared a little pdf about the topic with detailed mathematical explanation, which can be found here, and also below in the spoiler tag as images:
EDIT: The calculations were flawed, which resulted in wrong conclusions. I corrected them, now they should be all right.
EDIT2: There are still some minor issues with the calculation of the Zerg delay. Will check shortly.
EDIT3: Checked again, I think conclusions should be about right.
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There are two important conclusions here to say:
1. If you are a Protoss player and you see your natural Hatch blocked, you have two options. Either you want to kill the Hatchery as fast as you can, resulting in as little time delay as possible. In this case, you should pull all your Probes, but it will cause you to lose more mining time than optimal. I only recommend this if you want to hit a very crisp timing which fails even at the slightest of delays.
The other option is to kill the Hatchery with as little mining lost as possible. Surprisingly, that does not coincide with the fastest killing of the Hatchery. In this case, you have to pull 8 Probes (provided that you discovered the Hatch very shortly after having been placed). This will result in more time delay than optimal.
A good compromise between the two is to bring about 11-12 Probes. That way you will not lose much more minerals than optimal, but you can reduce the time lost quite effectively.
In any case, make sure that your opponent won't plant a Hatchery again.
2. Hatch block is no superweapon. It won't give the Zerg player suddenly a tremendous lead, but it will give a slight advantage in both time and minerals, even if the Protoss reacts properly.
So this is my answer, agsub, I hope it suffices . If anyone has any comments, ideas, criticisms, I am open, as always.
Also check out my previous works as well:
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