A product market fit lesson — 80 users. That’s how many users Burbn had at its peak. Even though the app had close to 100 true fans, the one telltale sign that Burbn was not on track to product market fit was minuscule conversion. For users, the app was far too complicated and did too much. With Instagram, 25,000 users showed up the first day. So what changed? First, Systrom recognized that Burbn was…