Having watched the cr<->CE exchange more closely over the last several weeks, it appears that it needs to have a bid increment added. Any time someone places a buy/sell order on the market, require it to either match the current high buy offer (or the low sell price), or be at least 10 crowns further.
This would go a long ways toward fixing two problems we appear to be seeing:
1) Currently, the market spread between the high buy offer and the low sell offer is significantly more than the 2% trading fee. This is allowing arbitrage traders to make far more crowns playing the market than playing the game. This, in and of itself, isn't a huge problem, but it appears to annoy a lot of other players when arbitrage trades are made in large blocks.
2) Currently, the market isn't reaching the clearing price quickly enough. That is, when the supply and demand changes, the price of the current market may be significantly off and single one-up bidding is too slow to adjust. This lets people "push around the market", when really, all they are doing is pushing the market in the way it should go anyway.
Edit: Besides implementing a bid increment as mentioned above, I can think of two alternatives that do effectively the same thing. First, you could require all bids to end in a zero, so 4930 would be a valid bid, while 4933 would either be rejected or rounded down to 4930. Second, you could reduce the blocks of CE traded from 100 to 10. You would, of course, have to adjust all current trades. This would also require people to trade in larger numbers of blocks than the do now.