If you're a whale and want to dump a big position:

Step 1: Pump the market by small buys on light volume and drive the price up.

Step 2: When the suckers see the run up and think that they can get rich quickly, then dump as quickly as you can before the market falls too much.

Step 3: Repeat.

Of course, this only works so long as there are enough suckers who will buy as the price is increasing.