The author makes good points here. While it's true that YC and other venture investors invest in many companies to increase the chances of large returns on the best of their portfolio companies, there is another significant advantage to YC having a bunch of companies in each batch - the teams that are not doing so well are a source of talent for the teams that are doing well. At some point YC can and has encouraged teams they think aren't making enough progress to join teams that are. A friend in one batch described his batch consisting of: 1/3 working on great ideas/products that could be big, 1/3 working on mediocre ideas/products and 1/3 working on bad ideas/products, and those in the bottom 1/3-2/3 still had good team members that could be sourced for talent for the best 1/3 and for previous YC companies doing well.