I'm familiar with an organization that lost about $750,000 because someone spoofed an email from the CEO to the CFO asking to wire money to an account. The CFO fell for it. AFAIK, the money was never recovered (nor was the CFO fired... it was all just chalked up to 'the cost of doing business').

That was with NO crypto/signature spoofing involved... if the CFO has now been trained to not act on large dollar amount requests from the CEO without at least checking a digital signature... perhaps the CFO would be more likely to fall for it now since he has been "trained" that cryptographic signatures are a sign of authenticity?