Not everyone who is selling large amounts is a 'price manipulator'. I got in early on vertcoin and was able to grab about 3k vert with only 3mhs hash power. I dumped these when vertcoin first started to get popular and the price was high. I definitely wasn't a 'manipulator.' Just trying to minimize my risk and sell the coins while they had worth. THat might be what you are seeing with these walls - just redistribution of the coins, which is good for the coin.