When you are talking about an early startup I think it is a reasonable assumption to say that loss of anyone on the core team is going to kill the startup. It

When you are talking about an early startup I think it is a reasonable assumption to say that loss of anyone on the core team is going to kill the startup. It might not die as quickly as a shop run by a solo founder, but it is on deaths door and knocking loudly. The only real benefit I perceive in a team over a sole founder is psychological; with co-founders you have people to challenge you (challenging both your assumptions/decisions and challenging you to constantly perform at a high level of productivity.) The biggest killer of solo startups is not accidents but rather frustration and fatigue, with a team you can have someone to pick up the slack if a founder starts getting burned out and you have someone to vent with when frustration levels start to rise.