The sad lie of mediocrity
http://sethgodin.typepad.com/seths_blog/2008/11/the-sad-lie-of.html

The Sad Lie Of Mediocrity by Seth Godin

Doing 4% less does not get you 4% less. Doing 4% less may very well get you 95% less. That's because almost good enough gets you nowhere. No sales, no votes, no customers. The sad lie of mediocrity is the mistaken belief that partial effort yields partial results. In fact, the results are usually totally out of proportion to the incremental effort.