While asking, Should 'Bad' Financial Contracts Be Replaced with 'Blessed' Ones?, Steve Waldman makes an amusing aside about common stock:
No rational regulator concerned with substantive transparency would approve of common stock, if it were a novel investment vehicle. It guarantees no cashflows whatever, its “control rights” are so weak for most purchasers that representations thereof should be viewed as fraudulent. Empirically common stock behavior is very weakly coupled to the performance and health of the firms that stocks fund. The only instrument in wide use more substantatively opaque than common stock is fiat money.