[snowfox]

I have no experience on hardware startups. But my gut feeling is that they do have additional layers of complexity relative to pure web startups. As such it makes sense to have somewhat more co-founders than web startups.

However, the more people you add to a team, the slower it moves and the team dynamics grows exponentially. It will reach a point after which you get diminishing marginal gain, or even negative gain.

For a startup I believe agility is critically important. I would be worried to add too many people from the outset because it is difficult reverse it. It's hard to 'unfounder' a cofounder later on. My advice is to have a core team of 2-3 cofounders to see how it goes. If you really feel insufficient after a while, bring one in one at a time. It is less risky than having too many in the beginning and discover problems when it's too late.