Large investors in recent public offerings have been told that when lock-ups end on selling the shares, blocks of shares must be privately sold rather than be dumped onto the market.

"You can't not have Banks, and you can't not have trading," an executive at a big private-equity firm said to me. "Part of the value in a stock is the knowledge that you can sell it this afternoon."

These costs have led some small companies to go private, hardly a victory for public oversight, and some foreign firms to withdraw their stocks from American exchanges.