One of those market makers is Equity Zen.
Equity Zen helps investors/employees in startups monetize their shares prior to an IPO by creating a secondary market for their shares by matching buyers with sellers.
They claim 900 investments closed for stockholders of over 40 companies.
With the IPO market tight these days, employees are waiting longer and longer to obtain liquidity and if the company, like Jet.com, gets bought before its market debut, it may take even longer.
Current Equity Zen investors include: angel investors, high net worth individuals, family offices and investment advisers.