Maybe a silly question, but why not introduce a fee for placing an order?
Let's say 50% of the current fee which we have to pay to the exchanges. The exchange gets the other 50% when there is a buy/sell.
This way ONLY the real asks and bids will be at the exchanges. No playground for people like Nemesis (if he's the right person), cause he'll lose (a lot of) money to place such an order in the first place...
I think it could be better for the near future of BTC (new money).
It´s actually quite the opposite. A lot of exchanges now use maker/taker system, which means that the own who placed his wall actually get´s paid for it cause he improves liquidity on the exchanges. Which makes sense in my opinion. There is nothing wrong with placing huge walls on an exxchange, it´s a free market, if someone wants to buy/sell into it, he can do. If someone is using it to manipulate the price he is risking his stash USD or BTC.
biggest problems are players who sell/buy into themself.
i dont see a problem in huge wall either, but buying/selling into your own orders should not be possible. but i guess this is impossible.