I wouldn't classify 1000 NEO as a sell wall. People are probably selling their stocks to either buy up a more promising venture or because they're shorting the market.
You think its conincidence that everytime Neo starts to grow a bit someone starts to dump hundreds and thousands of Neos? This started 9 hours ago. Just when Neo was starting to grow a bit a flatline appeared and stayed for 45 minutes at 540k until the price started to drop and it has dropped ever since. If that is not a "sell-wall" then nothing is. You can see it yourself from Neo one minute price graph in Bittrex.