I am lucky enough to work in a "internal open source environment" - I can and do search the whole code base for a major Fortune 500 daily for pieces that fit my needs. And I often find them - but the process of getting it refactored to fit my exact needs (and so improving their code and the overall reduction in entropy) is mostly impossible - because of humans No one is really willing to change someone else's code without talking to them, agreeing, getting past thier "yes I have tests but if you change it then I don't really know ..."

It's a fundamental problem - good well maintained tests help but this is cultural not technical problem.