Redundancy increases the resilience of living systems. More on this topic on www.resalliance.org.
The Berlin underground railroad system (S-Bahn) is an excellent example for poor resilience due to excessive "efficiency". When the harsh winter 2010 damaged a large number of trains, the entire system ground to a near-halt and restarted at a very, very slow pace. As of June 2011, the trains are still shorter, i.e. more crowded, than before. The reason: for the sake of "efficiency", S-Bahn management apparently reduced routine maintenance work and closed most of its repair workshops, laying off cohorts of expert staff. The few remaining workshops have been struggling to fix trains that broke down half a year ago.
The lesson: excessive "efficiency" kills "sustainability". Efficiency may also sabotage innovation, as Lukesch points out in a recent study on resilience (available in German here). You can be efficient when you know exactly what you're doing and which is the least onerous way of doing it. When you innovate, by definition, you cannot know exactly what happens next. Innovation means trying out new things, exploring untrodden paths, making mistakes and learning from them: all that looks quite wasteful when watched through "efficiency" goggles.
Does that mean that the much-revered OECD/DAC principles "relevance - effectiveness - efficiency - impact - sustainability" are mutually exclusive? In any case, it is useful to take a careful look at the assumptions behind these principles, and the way in which these assumptions come together - or not...