Are there any companies you had a chance to invest in but didn't, and in hindsight, would have been great investments?

Yes. You aren’t doing it right if you haven’t passed on companies that ended up being great investments. We have passed on about 1750 companies in the last three years and that only includes companies in which had some interaction i.e. meeting/call and not just cold email. Some of those are going to be great companies. Two particular examples that come to mind are Uber and Coinbase. I didn’t actually meet w/ uber but we knew enough people that knew the founders and/or invested in the seed that we probably could have made it happen if we pushed for it. I also took my first uber ride in late 2010 and was pretty into the service. I actually picked my now wife up for our first date in an uber five years ago. I just failed to see the grander vision of it not just being a luxury black cab service. Coinbase is another great company that we passed on. It is obviously not at Uber’s level yet but it has executed exactly how Brian (CEO) layed it out for me when we met after YC demo day. He basically explained Bitcoin to me and told me to by some and said if Bitcoin gets wider spread adoption, we will be the paypal of Bitcoin and they are well positioned to be that now.