There is a strong possibility the firms themselves have complained about the secondary markets and the private stock funds. If they became big enough, employees

There is a strong possibility the firms themselves have complained about the secondary markets and the private stock funds. If they became big enough, employees could potentially undercut their employer on future funding rounds. There is also the widely held belief that employees will work harder and be less likely to quit if they can't benefit from the appreciation of their shares until a liquidity event. Also, pricing in the secondary market by insiders could signal if a company is having troubles, something that they might otherwise be able to prevent from leaking out. You can see the results of these worries in facebook contracts that prevent current employees from selling their vested shares and the deal they struck in 2008 that allowed employees to sell only a 20% share of their vested options. If they were able to prevent ex-employees from selling their shares on the secondary markets they obviously would. So it would make some sense if the companies themselves are complaining about the practice to the SEC.