From Benjamin Pollack:
“There is a tremendous amount of spit and polish that goes into making a major website highly usable. A developer, asked how hard something will be to clone, simply does not think about the polish, because the polish is incidental to the implementation. ”
The quote was part of a response to a suggestion to duplicate Stack Overflow, and thus save subscription fees to the original. You can read Benjamin’s entire rebuttal, or Jeff Attwood’s succint commentary for more details. Jeff’s article in particular does a good job in summarising what “polish” entails, and by doing so makes it clear how such polish is integral, not incidental, to eventual success.