The Swiss currency shock has raised an awkward question many investors have been fearful of asking – what if central banks become as unpredictable and fallible as they are powerful? The Swiss National Bank’s sudden decision to abandon its three-year-old cap on the franc – the “cornerstone” of its monetary policy just three days before – led to the biggest one-day move in major exchange rates in the post-1973 floating rates era. To some it was a warning sign of other U-turns, mishaps and possible failures by central banks still ahead, outcomes not fully appreciated by long-becalmed markets.