It is ultimately up to the IB to decide how much he or she wishes to rebate back, and further, how much he or she wishes to serve his clients. Sometimes there is actual value added on the IB's side; HFT Group offers some excellent customer support for example. Always keep in mind that the size of the discount isn't always the only consideration. Further it is ultimately up to the client to research the various offerings available (much like brokers!) and decide which appeals most to him.
That said, I think everyone's made their peace and we can get back to the substance of this thread: evaluating and reporting the pros and cons of ICM as they stand.
Offering the best commission discounts for the best broker: $1.50 / RTL Global Prime: