Too early to boss. If questions about feasibility, risks and supporters have no answers yet, you are too early.
Dreaming for too long. The idea is starting point, and the end result does not yet have to be thought out in detail. If dreaming takes too long, the first supporters drop out while newcomers want to have all the discussions all over again.
The pioneer syndrome. The promoter has everything figured out and leaves no room for input from others.
Creating support. People feel no connection to their own concerns and ambitions and are not allowed to go through their own thinking process because the outcome is already fixed.
Budget-driven collaboration. If money is the main driver of cooperation, you can expect trouble.