Correct, most secondary markets only allow accredited investors. My point above is not that secondary markets are allowing the general public to buy shares, but

Correct, most secondary markets only allow accredited investors. My point above is not that secondary markets are allowing the general public to buy shares, but rather, that secondary markets are a path to an IPO - i.e. if you were an accredited Goldman investor who bought in at a $50b valuation, you're likely hoping for a FB public offering to drive the valuation up to $75-100b so that you can dump your shares and double your investment.