tyre pressure can effect a car as much as the tyres you run!

normally for small cars/normal tyres you would use between 32-36 cold.
more for low profile's, at least 36.
however as others said, for every application there is different optimal pressures.
ie drag = lower psi is better
4wding = lower psi(this has been debated though, seems high pressure is good too!)

ie if someone wants to achieve a specific outcome, or are running an upsized package, then they would use such a high pressure, but this is only when you know about the effects and differences it causes on handling, traction so on...

oh last note, Dont drop your pressurres to 32-36 after a long drive, remember hot air increases pressure!