Two connected suggestions:
1) Login verification via SMS to a mobile phone.
As used by Google and recently announced by Twitter: https://blog.twitter.com/2013/getting-started-login-verification
Though I am not sure what the financial implications of this would be.
2) Social login - encouraging users to login with their Facebook, Twitter, Gmail accounts which have already had some sort of Login Verification or are connected to a "social graph" that can be checked.
Paul