This is a fascinating line of thought and, at least from a game theoretic perspective, seems to be a mechanism for creating automatic, passive collusion between

This is a fascinating line of thought and, at least from a game theoretic perspective, seems to be a mechanism for creating automatic, passive collusion between companies. If we model the market as a prisoner's dilemma where a lawyer is deciding whether their client should defect or not, mutual defection is the normal Nash equilibrium. But if both lawyers are representing the same client then cooperation becomes the dominant strategy: regardless of what the other lawyer does (cooperate-defect and cooperate-cooperate both have higher total payoffs than defect-defect). Notably, this mechanism is entirely passive: it requires no communication between managers or even managers and their investors. Merely knowing that my investors are also investors in my biggest competitor would make "cooperation" the dominant strategy without requiring any conscious collusion. Taken to the extreme, this actually undermines the entire free market: every manager in a 2+ place firm would have a fiduciary responsibility to drive their company out of business so that the first place firm could enjoy monopolist profits (and thus maximize their shared investor's total return).