Three Personality Traits of The Ideal Co-founder

After working with a lot of potential co-founders who didn't quite fit
the bill, I've distilled the ideal co-founder down to three core
characteristics:

1) Smart
2) Trustworthy
3) Hardworking

This may sound obvious, but the core problem is that a lot of
seemingly great people only fulfill two of the three. Which means that
they won't work out as your cofounder. I think that the definition of
each characteristic is pretty self-explanatory, so I'll describe the
trait combinations that don't quite work.

QUICK NOTE: These are caricatures. Everyone will probably have one or
more of these to some extent. The thing that really matters is the
magnitude of that extent, and how the flaw interacts with your
personality.

Smart and Hardworking (But Inconsistent)
You meet this guy (or girl), and you can see the spark in his eyes. He
has lots of interesting ideas, and is always in a rush to implement
them. The quality of his work is high, and he seems like he is going
places. But there is something about him that you just don't quite
trust. Maybe it's something concrete (like constantly being late, or
blowing you off inexplicably), or maybe it's just a feeling of unease
in the pit of your stomach. Whatever the case, this isn't going to
work. One day, this guy is going to sell you out when something better
comes along. Or he's going to exploit your work and then use a
loophole to con you out of your equity. Soak up everything you can get
from this guy, but keep your eyes on the knife drawer

Hardworking and Trustworthy (But a Bit Inept)
Honestly, this combination is the hardest to ditch. This guy is sweet
- he's obviously super-loyal, and he works tirelessly. But... his work
isn't quite what you could have produced. When you give him a task
that you could have finished in a day, he finishes it in three or four
days. And he needs a lot of direction - the only way to guarantee that
his work is top-quality is to hold his hand through all of it.

This guy could be a great employee at a larger company, but he just
won't cut it as a cofounder. The startup needs to move fast, and
everyone needs to contribute on a reasonably equal basis. Some
cofounders will be unable to do the work that you do because they have
a completely different set of talents, and that's fine. But, when
there is a lot of overlap, you should feel like your cofounder is
roughly equal to you, if not better in many respects.

Smart and Trustworthy (But A Bit Lazy)
You geninely enjoy being around this guy, and he has so many great
ideas. He can think through literally anything - you're sure that you
and he are toe-to-toe in the brains department. But he doesn't get
that much done, unless you push him. I'm sorry to say it, but this guy
is lazy. At a large company, he could be at home in the strategy
department. But, at a startup, there are no strategy roles. Everyone
needs to be building or selling the product at all times. There is no
place for the non-self motivated. It's a tough world out there.

Conclusions?
So, something I've realized is that there is no perfect cofounder.
Everyone has one or more of these flaws. They are either inconsistent,
inept, lazy, or a combination of the above. As an aside, when I say
inept and lazy, I'm talking about a lot of people who would be
considered brilliant and hardworking in comparison to 95% of the
people out there. It's important to be honest about everyone's flaws
(including your own), and to find people whose talents complement your
flaws. Maybe you are lazy, and can find a cofounder who is happy to do
do your work. Or maybe you are inconsistent, and can find someone who
is trustworthy and won't double-cross you (until you find someone
better).

This is one major reason why the smart money in the startup world
suggests that you date your cofounder before you take the plunge.
After dating, joining, and even splitting from a bunch of cofounders,
I can say that you need to tread carefully...