Let me preface this question by saying: I know it's only rep, and moreover, only on Area51, so who really cares?
Thus, I'm not asking out of a sense of justice, but of curiosity.
Today, I have 1,209 rep. Yesterday, I had over 1,800 (1,819 if memory serves).
I've experienced random "adjustments" of rep before, which may have "lost" me 10-50 rep... but 600?
Was there a massive re-calc, or change of rep rules here on Area 51 in the last 48 hours?