Notes:
Simplicity is hard work – and I don't think it always maximises “the amount of work not done”. I (and others [Jon Kern, Alastair Cockburn]) am reminded of Pascal's “This letter is longer than I wish, for I had not the time to make it shorter”.
I don't really have an insight into what is intended by this principle, I can only offer the followign anecdote...
On a recent project I was asked to help choose a strategy for auditing activity within the system. The problem arose because the requirements for reporting had not been captured – and the developers were trying to design something flexible enough to address all conceivable needs. (They deserve credit: they knew enough to realise that what they were considering was complicated, and they sought help!)
My solution (which was “obviously right” once stated) was arrived by the consideration that “doing nothing” is the simplest thing. That is, for now, just make a note of the interactions that need audit information recording. Later, once the reporting requirements are known, come back and record the appropriate information.