> Companies which explicitly hold other people's money are usually held to higher standards in holding it (Solicitors, Banks, Estate Agents, etc). For example deposits are usually held in a client account, separate from other corporate funds, and not usable except for the intended purpose.
Banks use client deposits to fund their lending, though.
I don't see any fundamental problem with mixing client and corporate funds, provided there is good accounting, solid auditing and sufficient oversight in place to ensure client funds don't go missing. Obviously none of those existed in Mt. Gox.
Banks are pretty much the only institution that's allowed to commingle client funds with their own funds, and they're subject to a whole bunch of extra regulations and scrutiny as a result. Indeed, I've seen people argue that being able to do this is basically what defines a bank.
Banks use client deposits to fund their lending, though.
I don't see any fundamental problem with mixing client and corporate funds, provided there is good accounting, solid auditing and sufficient oversight in place to ensure client funds don't go missing. Obviously none of those existed in Mt. Gox.