I was just thinking about a St. Paul, Minnesota Qualified Intermediary (QI) that commingled it's exchange funds, then filed for bankruptcy. It turns out that the QI was day-trading with the client's funds. During the bankruptcy proceedings the court appointed trustee treated the pooled exchange funds as a bankruptcy asset. This bankruptcy asset was then available to all creditors in satisfaction of debts owed!
A separate account for each exchange client is sound protection against attachment by the courts. Be sure that the QI separates them at the bank level and have them prove it. Ask for online (view only) access, through the bank's website, not the QI's for independent verification!
Again whether it's you or your client doing the exchange, due diligence is important.