“It was a neat idea that’ll never happen, and I have nothing else to say about it.” So said JPMorgan Chase chief executive Jamie Dimon on Friday, giving Facebook’s Libra cryptocurrency project one last kick at the end of what had already been a brutal week.  Industry sources have told the FT that the decisive factor was a letter that Democratic Senators Sherrod Brown and Brian Schatz sent to Mastercard, Visa and Stripe. It warned that proceeding with the project would expose even their non-Libra businesses to heavier regulatory scrutiny.