I don't know if I'm right about this, but it seems such an exchange might contribute to something like 2008. Then, it was the common man investing in over-heated real estate; now, it could become the common man investing in over-heated tech.
I feel like those who work in tech often forget that it can fail, have cycles of boom and bust, etc. like any other industry.
Of course, I do think it can serve a useful purpose, but there is reason early-stage, private investment is restricted to qualified investors.