My example is not contrived, it is literally this exact post (and HN isn't the only site with publicly available information). However, I agree with you - sens

My example is not contrived, it is literally this exact post (and HN isn't the only site with publicly available information). However, I agree with you - sensitive information should not be easily guessable even if other security mechanisms are in place (and they absolutely should be of course). What I am really reacting to is rules of thumb - "always do X and you will be ok". The issue is, it is often easier (and far more valuable) to understand the real reason behind things than to remember the rule of thumb.