The Swiss central bank stunned investors and traders the world over on Thursday when, with no warning, it abandoned its three-year-old currency peg of 1.20 francs to the euro.
The peg was the crucial part of the Swiss effort to hold down the value of the franc against the ever-weakening euro as nervous investors fled the euro and volatile markets for the safe-haven of Switzerland.
A too strong franc would hurt the country's export-dependent economy and raised fears of deflation falling import prices, given oil and commodity prices were already tumbling.
Why only last month, the SNB reiterated a pledge to continue to support the franc floor by buying the euro in "unlimited quantities" if needed.
So why did the Swiss suddenly abandon the franc floor?
In short, likely because the extent of the euro's decline made the plan too risky and too costly to continue.
The European Central Bank is expected to announce when it meets on Jan 22 a massive bond-buying programme (dubbed QE for quantitative easing) to pump money into the region's troubled economy.
Before Thursday, the euro had already sunk to a nine-year low against the US dollar as the two economies increasingly diverged: A stagnating Europe looking to flood its economy with even more cheap money and a strongly recovering US with plans to raise interest rates.
According to the Telegraph, at one point the Swiss were buying half the entire sovereign bond issuance of the eurozone to maintain the franc to euro peg. While this reserve accumulation subsided for a while, it was building up to a new crescendo as money poured in to Switzerland from Russia, and fears of Greece exiting the currency bloc returned.
If, or when Europe embarks on a huge QE - printing more euros to buy bonds - it will weaken the euro further, making it that much more difficult and costly for the Swiss to buy enough euros to maintain the value of the franc cap. Some of those new euros would also flow into the safe-haven franc.
The Swiss central bank on its part just said that the divergence between the US dollar and euro is "a trend that is likely to become even more pronounced", but it thinks the franc is no longer as overvalued as it was in 2011, so the cap can go.
But its abandonment of the peg seems to confirm that the ECB's QE is coming next week and it's likely to be a big one.
Carl Weinberg, chief global economist at High Frequency Economics, told the New York Times: "We can only guess at what was in their minds. But maybe they are afraid that the euro is coming on some hard times, and they didn't want to be tied to a sinking ship."
So what's the franc fallout?
1. Euro got hammered
The currency shared by 19 European economies including Germany, France and Italy, suffered its biggest one-day drop against the Swiss franc in history and skidded to an 11-year low against the U.S. dollar.
The loss of Swiss support sent the euro as low as US$1.15675 on Thursday, the lowest since November 2003. It recovered a bit of ground on Friday to last stand at US$1.1645.
2. Swiss franc soars and Swiss stocks collapse
The Swiss central bank simultaneously cut interest rates when it scrapped its currency peg, hoping to offset some of the damage in foreign exchange markets. But that was too little to stop the tide, as the franc jumped nearly 30 per cent against the euro on Thursday.
Swiss stocks also plummeted in value, as investors hastened to sell shares - of exporters in particular - priced in francs. Shares of Swatch, the global watch brand, fell 16 per cent, leading an almost nine per cent fall in the Swiss market index. But the decline was broad-based, including food giant Nestle, cement maker Holcim, chemical company Syngenta.
Investment bank UBS said the shock move could lead to a loss of 5 billion francs worth of exports and knock 0.7 percentage points off the country's economic growth.
3. Swiss-made products suddenly became a lot more expensive
Not just Swiss watches and chocolates or that skiing holiday but cement and machinery and chemicals.
"Words fail me!" Nick Hayek, the chief executive of Swiss watchmaker Swatch, said, calling the move "a tsunami; for the export industry and for tourism, and finally for the entire country."
4. Investors rushed to buy gold and yen as a safety against volatility
Gold and yen were already up this week on anticipation of Europe embarking on massive QE, the World Bank cuting its 2015 global growth forecast and the collapse in oil prices sparking fears of deflation.
On Thursday, gold for immediate delivery jumped 2.8 per cent for the biggest increase this year.
"With the Swiss National Bank making such a dramatic move to get out of the way of the falling euro, it's part safety trade and part asset protection given the devaluation of the currency," Michael Cuggino, president of Permanent Portfolio Family of Funds, told Bloomberg News.
The franc fallout also sent the yen headed to its biggest weekly gain versus the euro since May 2011
5. There are winners and losers
First the losers. They include retail investors and traders in foreign exchange markets who were playing a highly leveraged and dangerous game betting on the franc, to the many Croatian and Polish homeowners who took out mortgages in the franc.
FXCM, one of the biggest foreign exchange trading platforms for individual investors in the United States, said its clients lost US$225 million on Thursday because of "unprecedented volatility" in the exchange rate of the euro against the franc. Another online foreign exchange broker in New Zealand said it was shutting down because heavy client losses saw it breach regulatory capital requirement.
The winners include anyone with Swiss assets - and some 280,000 people working in Switzerland but living and paying bills in euro-using countries like France, Germany or Italy who immediately saw their incomes jump 30 per cent.