The liquidity of startup shares has gotten better in recent times. I'm an engineer at http://www.equityzen.com, a marketplace for pre-IPO shares, and I believe more shareholders are starting to see that selling before an exit is a viable option for faster liquidity.
We helped lobby and push for this bill and I'm glad to see it making progress in providing better options for startup employees.
The second market is a bandaid. In addition to sub-par prices there's a huge bottleneck in the demand for shares, which is extremely volatile. And if cofounder X decides to offload 10% of his shares it'll wipe out any demand there is.
Equity is awful for a lot of reasons, but I'll never be convinced second-market selling is the panacea.
We helped lobby and push for this bill and I'm glad to see it making progress in providing better options for startup employees.