Which would you think would be better? They get trade fees or charge for cashing out/in?
There should be an option for both, so they can choose the amount of each type of fee (which could be 0).
Thats not entirely true, although I'm on your side as I think its pointless, Intersango's new fee structure does make business sense: it delivers on the goal of reducing spreads. Their thinking is a tighter spread will lead to more customers. For those who unknowingly sign up, the buys will be more expensive then they expect. I think this is stupid, however it has made the exchange favour sellers. If you dont mind using two exchanges, you can use this to your advantage for your trading activities.
The tighter spread is illusory because what customers gain in the spreads they lose in the fees. For an ordinary customer which just buys or sells and is not a maker, the fee is 0.95%. Intersango may be hoping that the customer will think, "Hm, the fee is sometimes 0.35% and sometimes 0.95%, this is all very confusing, let's say it's 0.65% on average, and the spread is pretty good too, let's join". I am not of the opinion that defrauding your customers should be called "business sense".
The new system actually discourages participants from accepting a highest bid/lowest ask. Instead it encourages the order to be off that by 0.00000001 BTC (or whatever the lowest increment the market supports).
If everyone is informed, there shouldn't be a functional difference from the symmetric system, just the displayed numbers will be different. In the symmetric system you have the same dilemma - if instead of accepting an existing order you place your own order, you stand to gain a more favorable execution price, but you risk the market going in the opposite direction and losing the opportunity to execute.
Hopefully the market throws a warning like "your commission if you click okay will be 0.095% which is equal to $x.yy . So the newbies don't get surprised.
If you add needless obfuscation people will be more confused, there's no way around that.