The drops are fast yes. Often drops can wipe out months of gains in just a few minutes.

The system is not managed by anybody. There is no situation where the system will "take" money from people converting steem dollars to STEEM. The system calculates the value of the STEEM over a 3.5 day moving average. From the moment you start converting. If the market has an aggressive down move, then your average conversion price may be a little higher than current market price and thus be a slight loss. Do not assume that "someone" is taking your money however because that is simply not the case.