Reason #1: you need an accurate, critical second opinion. If you start a company by yourself, you don’t have anybody that can give you an accurate second opinion. Oh sure, you can phone a friend every now and then, but they’re hearing your story about the business – which is often very different than the facts. You’ll tell them the facts that support your decision, omit the ones that don’t, and they’ll give you a second opinion that matches your decision. Not a big surprise – but sometimes, a very big failure.
They also need to be critical – not just yes-men with the same point of view. If you’re a singer trying to build a rock band, you don’t build the entire band out of singers. You need people coming from different backgrounds with different perspectives, and yes, that’s going to mean disagreements.
But it works.
When Keith Richards was asked how the Rolling Stones worked so well together for so long, he answered, “Friction, baby.”
I loved that answer so much that before my days of personal branding, I chose Friktion as my name in Yahoo Messenger. (Wow, that was forever ago.) I never wanted yes-men around me – I wanted people who could pull me aside and say, “Wait – the jazz hands are all wrong for this song. It’s a love ballad. Maybe just hold a candle for this one.”

Reason #2: you need to divide tasks to match passions. Starting a company is a lot of work – you’re going to have to handle attorneys, accountants, marketing, sales, product design, delivery, customer support, hiring, management, and much more. The founders may have experience with some of those tasks, but not all of them. Even throwing in 2-3 cofounders still isn’t going to cover all of your bases.
You’re still going to have to do work you suck at.
But sometimes, that work is actually enjoyable.
Even though I sucked at sales, I loved doing it, and it actually energized me. Managing people, on the other hand – I suck at it, and it drains the life blood out of me. Thank God Kendra enjoys tackling that stuff.
The more diverse your cofounders are, the more likely somebody’s going to enjoy doing a task you hate. That keeps everybody happier longer, and you need that happiness because starting a company is hard.