[tomatocracy]

I think it's probably more about hedge funds etc where they will negotiate bespoke terms/pricing across the board (including assessing risk which at that level might partly be based on track record, identity of the underlying investors, strategy etc).

[beezle]

Once the amounts get lumpy there needs to be complete assessment of counterparty risk (you). IB can't assume that you are only borrowing from them and that the collateral in your account won't first be liened by another party, etc.