The oil boom / bust is a good example, and you can see from their recent change in correlation, we may be seeing the last weeks of those two assets moving roughly in tandem. The last time the correlation movement was this unstable was 2008/2009 - when they transitioned from uncorrelated to correlated.
FIrst, let me explain what is charted here: on the top is the SPX weekly. In the middle is an indicator I wrote that tracks the correlation of price movement between two symbols (see the linked post for explanation and source code). Bottom is a smoothed . On the left is 2008/2009 and on the right is today.
If you remember 2008, equity prices faded gradually until summer and fall when the crash occurred. Gas prices were relatively high until the crash kicked in. By the election, gas prices were depressed because of economic panic. Once Q.E. kicked in, oil (along with almost all ) started to rise as did the SPX . That basically continued until Q.E. stopped last year. You can see that in the correlation indicator - in 2007/2008 the SPX and oil weren't correlating well (red background) until the economic panic caused both to crash. By 2014/2015 they are correlating (green background). But you can see the correlation becoming less stable as 2015 got underway and oil prices started their fall from 100+ a barrel. By summer the sustained change in correlation movement had the relationship inverted for a few months (the red band). For a short while it looked like equities would shake their Q.E./commodity addiction and get back to tracking a truly expanding economy (and not just an expanding money supply), but stocks soon followed oil .
The question is - will equities (and the economy) manage to to see expansion that isn't FED induced? Throughout the late 1980s and 1990s, the US economy saw sustained expansion while went lower and lower year after year. Money supply was stable and grew in step (for the most part) with the underlying economy as a mostly hawkish FED tactically adjusted rates around curbing inflationary pressure.
US policy makers (The FED) continually mention that they see the economy expanding and will raise in a regime that tries to resume the "normal" of the 1980s/1990s. Remember - there was a time that lower commodity prices (mainly oil ) meant more money in consumer's pockets which led to further economic expansion. But market continues to indicate that the Q.E. heroin addiction is a hard habit to break with some ugly withdrawal symptoms.
Remember - liquidity is what drives markets higher. Where you get that liquidity (either from money printing or from actual wealth creation) matters in the long run. Money printing isn't sustainable whereas wealth creation (eg - actual economic expansion, higher productivity, and the lot) is sustainable as long as inflationary/speculative pressure is contained.
So the question is: Will a junkie become an athlete? We will soon find out, but expect more in the process as people readjust habits throughout the economy and markets.