Kraken, the cryptocurrency exchange preparing for a potential public listing in the U.S. early next year, has seen the departure of four senior executives from the institutional side of the business, according to a person familiar with the matter. Those who have recently left Kraken are: David Olsson, global head of institutional sales; Shannon Kurtas, head of exchanges and a VP of product and the Pro service; Jeff Kramer, a director of OTC trading and Sanjay K, OTC trading lead for Americas, the person s ...