The machine was originally invented by one Trin Tragula in order to annoy his wife. Because she was forever nagging him for having no sense of proportion, he decided to invent something that would show her what having a sense of proportion really meant. Unfortunately the shock of being placed in the Vortex destroyed her brain, but Trin Tragula's grief was tempered by the knowledge that he had been right and she had been wrong. The Total Perspective Vortex had proved that in an infinite universe the one thing sentient life cannot afford to have is a sense of proportion.
Only Zaphod Beeblebrox is reported to have survived the Vortex unscathed (and to have eaten the small piece of fairy cake). This may be due to the fact that he has an ego the size of the universe, or more likely that the Vortex he entered was in fact in an artificial universe, which had been specially created for his benefit (thus making him the most important being in it).