How do ROFRs and transfer restrictions impact secondary market liquidity?

I'd say the landscape in Europe is pretty similar to the U.S. and companies mostly engage in these kinds of restrictions to protect themselves.

If you look at the secondary markets historically, pre-2000 bubble, it wasn't much of a problem—because either you didn't get equity or you’d have an IPO in a few years. 

After the bubble, companies like Facebook and Google became flexible on letting employees transact, leading to the creation of SharesPost and SecondMarket. That backfired for Facebook when they had over 500 shareholders and had to go public, which then scared the Valley and the next generation of great startups —Airbnb, Pinterest, Uber, and so on. 

Those companies made it a rule to block every secondary transaction, and so we saw the rise of platforms like Forge where you could do forward contracts, so the companies didn't really know that employees were selling.

Today, we see a maturing ecosystem where companies understand that they need to organize the market themselves and be at its center. 

When talking to founders, what we realized is no one is really against secondary. They just don't want people trading with anyone. They want control over their investors, they want to keep the right incentives with their team members, and they don’t want to publicly share information.