Having just read about Equity Zen following your comment, I'd also be interested to know what people think about them. Their FAQ lays out a pretty compelling case for their value prop to all parties, so I'm curious if there are any strong arguments against them, especially from a company's perspective.
I can put my spin as a buyer on it. Overall it's pretty good although fee are high. The other thing is they do specialize in forward contracts which kinda suck but only option to buy shares of companies that do not allow transfer right now.
