Should people ask for permission or ask for forgiveness when breaking the rules?

People often say that "it's better to ask forgiveness than to ask for permission" when excusing their own rule-breaking. I hate the phrase, but I can't put my finger on what's so objectionable about it. So what does the phrase mean? Is it right or wrong? If it's true for some organizations, doesn't that indicate that the organizations's rules or policies are somehow bass-ackwards?