make -j optimization

[David Kramer]

In GNU make, you can specify a -j <n> option, to run <n> commands 
simultaneously.  This is good.

I'm having an argument with a coworker over whether specifying a value for 
<n> greater than the number of the processors in the system actually does 
any good or not.  I don't see how it can.  In fact, specifying one fewer 
than the number of processors shoudl have almost the same performance as 
specifying the number of processors.

Thoughts?