In the Big Short Danny Moses was not going to do the deal (to short mortgage backed securities) until he got the answer to a question from the bank's sales person:
> I'll do it, but only after you explain to me how you are going to fuck me.
Seems like an appropriate question whenever dealing with an investment bank.
Actually, slightly rephrased, it's a reasonable thing to consider for any non-trivial interaction: "What are your stakes here?"
Even with the best of intentions, people are complex and complex transactions between two or more of them are complex-squared. Taking the time to make sure both parties understands what the other does and doesn't bring to the table is important for success.
> I'll do it, but only after you explain to me how you are going to fuck me.
Seems like an appropriate question whenever dealing with an investment bank.