Robin is absolutely wrong, because different instances of human suffering cannot be added together in any meaningful way. The cumulative effect when placed on one person is far greater than the sum of many tiny nuisances experienced by many. Whereas small irritants such as a dust mote do not cause "suffering" in any standard sense of the word, the sum total of those motes concentrated at one time and placed into one person's eye could cause serious injury or even blindness. Dispersing the dust (either over time or across many people) mitigates the effect. If the dispersion is sufficient, there is actually no suffering at all. To extend the example, you could divide the dust mote into even smaller particles, until each individual would not even be aware of the impact.
So the question becomes, would you rather live in a world with little or no suffering (caused by this particular event) or a world where one person suffers badly, and those around him or her sit idly by, even though they reap very little or no benefit from the situation?
The notion of shifting human suffering onto one unlucky individual so that the rest of society can avoid minor inconveniences is morally reprehensible. That (I hope) is why no one has stood up and shouted yeay for torture.