In my own experience, item #1 is by far the most critical of all reasons listed. It's big enough to have pages and more pages written solely about it. I was the

In my own experience, item #1 is by far the most critical of all reasons listed. It's big enough to have pages and more pages written solely about it. I was the technical lead of an "educational platform" being developed and most of its products. As soon as two of the co-founders - out of 5 - found themselves jobs and other full time activities things started to go downhill very fast. One of the most annoying behaviors those then absent co-founders started to display was a sense of: "Why are you asking me that? Isn't this [feature/decision/scope] too obvious for you?". Hey, it's not a matter of being obvious or not; but still current or valid according to project's timeframe. I can't even elaborate on the amount of energy we lost.