gwraigty
Thinks s/he gets paid by the post
The only reasons I can think of why you would want to separate your CMA from your brokerage are:
Margin and float. If the timing of your trades is out of whack you could be drawing on non existent funds to pay your bills resulting in a margin debit.
Security. Do you really want a debit card tied to your brokerage account?
I had a debit card tied to a brokerage account at one time. Not now. I wonder though, how much would be at risk? I'd think just the cash in the settlement fund.
Some people keep large balances in their checking accounts. Same thing as far as debit card risk is concerned.