Looking at this datasheet for a mains switch, the 'preferred option' (5503 on the sheet) is called 'switched neutral'. I cannot see how both the live and the neutral can be switched with only 3 pins, as surely you need four (two for input live/neutral and two for output live/neutral) which leads me to believe that only the neutral is switched in this arrangement.
I also don't see how the circuit diagram makes sense, as if the mains plug is connected to pins 2 and 3 then this should just give a short across them when the switch is closed. If instead the mains plug is connected to pins 1 and 2 then only one of the live/neutral can be switched (depending on which one is connected to pin 2).
As only switching the neutral sounds like a terrible idea, combined with the lack of understanding of the circuit diagram, this leads me to assume I have misunderstood something quite badly. Any help you could give me in this matter would be greatly appreciated.
EDIT: The only way I can see the switch working properly is if we have the following setup:
Pin 1 Pin 2 Pin 3 (*) (*) (*) / \ | | / \ | | / \ | | / \ live live / \ mains circuit / \ neutral neutral mains circuit
as when the switch is closed pins 2 and 3 become continuous. This seems to disagree with the answers below, where pin 2 is the common neutral pin. Have I misunderstood the answers as well as the datasheet?