How many times in the last few days have we been told that Turkey - or Ukraine or Venezuela or Argentina - are too small to matter? How many comparisons of Emerging Market GDP to world GDP to instill confidence that a little crisis there can't possible mean problems here. Putting aside this entirely disingenuous perspective, historical examples such as LTCM, and ignoring the massive leverage in the system, there is a simple reason why Emerging Markets matter. As Reuters reports , European banks have loaned in excess of $3 trillion to emerging markets, more than four times US lenders - especially when average NPLs for historical EM shocks is over 40%.
The risk is most acute for six European banks - BBVA, Erste Bank, HSBC, Santander, Standard Chartered, and UniCredit
As Reuters notes, 
European banks have loaned in excess of $3 trillion (1.83 trillion pounds) to emerging markets, more than four times U.S. lenders and putting them at greater risk if financial market turmoil in countries such as Turkey, Brazil, India and South Africa intensifies.
But the exposure could be a headache for the industry as a whole, just as it faces a rigorous health-check by the European Central Bank, aiming to expose weak points and restore investor confidence in the wake of the 2008 financial crisis.
"We think EM (emerging markets) shocks are a real concern for 2014," said Matt Spick, analyst at Deutsche Bank. "When currency (volatility) combines with revenue slowdowns and rising bad debts, we see compounding threats to the exposed banks."
An emerging markets crisis could hit banks in a variety of ways - a collapse in local currency can hurt reported earnings or capital held in the country; loan losses can jump as interest rates rise; or income from capital markets activity or private banking can fall.
The biggest risk is that a jump in interest rates sparks defaults on loans, analysts added. Often a credit shock follows or replaces a currency shock, as happened in Argentina in 1999-2002.
they still have about 12 percent of their assets in emerging markets, and about a quarter of their earnings come from the region as often the businesses there are "unusually profitable", Deutsche Bank's Spick said.
...emerging market turmoil could also have a broader, indirect impact on revenues in investment banking and wealth management.
"A significant increase in volatility in EM bonds and FX may result in volumes drying up and hence a potential for a material slowdown in EM fixed income revenues," said JPMorgan analyst Kian Abouhossein.
He estimated the investment banks of HSBC and Standard Chartered each generated $2.1-2.2 billion from emerging markets, while Credit Suisse and Deutsche Bank made about $1.1 billion each.
Dismissing the "rotation from EM to DM" meme - we previously noted... 
The ironists among market punters will even attempt to construe all this as a reason to buy more developed world stocks on the premise that the money flooding out of such places as Thailand, the Ukraine, Turkey, and Argentina will be parked in the S&P and the DAX (perhaps overlooking the fact that the purchase price of these now-unwanted positions was most likely borrowed, meaning that their liquidation will also extinguish the associated credit, not re-allocate it).
The Goldilocks lovers will also tend to assume that any such disruption will serve to delay the onset of genuine tightening and may even induce further ill-advised stimulus measures on the part of the major central banks. Certainly Madame Christine Defarge – that tax-sheltered tricoteuse who knits beside the guillotine set up for the hated bourgeoisie – has already begun to militate for such a response.
For their part, the biddable are already trying to drown out the noise of the Cacerolazo by making the fatuous argument that the EMs account for such a piffling portion of world GDP that their fate should be a matter of complete indifference to the rest of us.
Needless to say this is a touch disingenuous at best. Their share of end consumption-biased GDP may be lower, but they account for an equivalent fraction, if not a small majority, of global industrial production – and they have been responsible for an even bigger proportion of its growth this past decade. Ditto for trade and ditto for resource use.