I have read one post where someone has said he was turned down by IB because he stated that he had less than 100 trades (it could have been 200 but I don't think so). I'm fairly sure that that post was on trade to win, not ET. Generally speaking, brokers are just covering themselves legally by asking how much trading experience you have. That said, some discount brokers that are tailored to experienced traders and have a minimum amount of trades/trading experience required.
Cheers,
TRADERguy