I learned this from watching our cohort evolve. Most of the really hyped companies that we felt sure to be successful no longer exist. Some of the least-known and most ‘under the radar’ companies (including Rainforest) are still thriving. While we mustn’t confuse correlation with causality, I do think that many founders that get into top-tier accelerators get distracted by building a personal or business brand, because so many new opportunities to do so arise as a side-benefit of being part of YC.
In my experience, only listening to your customer counts in the end. At Multiply.com we thought we were a social media company. It took us too long to understand that our users were using us as a craigslist with high res photos. Once we understood our users, we found a path forward.