absolutely not, in fact, that's one of the shortcomings of existing exchanges: they are also acting as "market makers", in a very limited fashion - they should be opening up to allow external entities to act as market makers.
if you are able to trade multiple markets at once, you don't need access to lots of cash - you just trade the markets and hedge positions against each other.
They most certainly are not. Market making means the exchange digs into it's own reserves to fulfill an order if they can't match a buyer and seller at the time, like the forex boys do, tell me one BTC exchange that does that?
In other words the Market Maker sells to and buys from the clients, it doesn't just do match ups.
http://en.wikipedia.org/wiki/Market_maker