Hayek said this about economics but I think it's applicable to everything we design. As an architect I have a front row seat to the limits of our ability to understand the consequences of our decisions, and I think it's fundamental. We get better at controlling for these unintended consequences, but we also seem to consume any advances by making our designs more complex (i.e. buildings used to be built with two or three materials, now it's literally thousands).
A theme I've noticed this year across multiple disciplines is the tendency of systems to be exploited in ways their designers didn't foresee. Informal agreements go by the wayside and once exposed become part of its regular use. I've noticed this in politics, legal contracts, games, the news, internet forums, etc. Historically a popular example of this is the gentleman's agreement that US presidents abided by - the two term limit that George Washington imposed upon himself - then FDR was elected to a fourth term; something no president had ever done. After his death Congress passed the 22nd amendment which limits presidents to two terms. Examples from 2016 might include: news organizations inability to convince readers of their legitimacy in contrast to fake news, the US Congress's unwillingness to review the president's Supreme Court nominee or Federal Reserve appointees, reddit's inability to deflect gaming of their algorithm, and internet service providers willingness to become 21st century robber barons. It almost appears that it's en vogue to break with convention and subvert anything that isn't specifically stated or enforceable legally.
If there's a take-away from me writing this it seems to be that as a culture we seem to be more accepting of this than previously. The spirit and intent of our contracts, systems, etc. seems diminished in relation to our ability to bend these systems to our will using their semantic deficiencies.
The tendency of a system towards entropy is also a law of thermodynamics - which may also be why life exists, so maybe this is actually more typical than the reality we've been living in?