I personally use it in corporate insurance business. Risk analysis of the client's portfolio, Drafting Risk slips, Policy wordings, Comparing multiple quotes and making a comparative quote chart for client presentation, policy audit... it just makes the life so easy..
Closing your source doesn't close your attack surface,it just closes the
community that would have helped you defend it. Security through obscurity
is a kind of tradeoff, not a strategy.. i mean that's what I feel.