Why is this so? I can see why it might be so for funded startups (since investors might take you more seriously if you have a cofounder), but does it also apply to bootstrapped startups? Should I really be worried if I'm planning on bootstrapping a startup with no cofounder?
A cofounder doesn't have to have equity or work on the project. They are the person you know who will be brutally honest with you. They have to have the ability to say, "This feature you love is stupid," and have you spend time deeply considering it. They take "you" and your author's bias (as much as possible) out of the startup.
And that's key, because if it works for you is irrelevant. It has to work for your market. No one, ESPECIALLY YOU, can say if that will be so. The best is where you can have the market itself give you feedback, but they are mostly incapable of enunciating what they truly want. So you have to guess. And when you do that, you need someone to help you winnow the chaff of what you like from the grain of what your market wants and needs.
Ofcourse, if the other person is a startup veteran, things are different but then they may not have enough time to go into details of your startup
But I've also started things with cofounders that didn't work out (I wouldn't say "failed" because they were more false starts than outright failures). You really do have to think of cofounding like a marriage, because you and your cofounder have to have the same set of goals. In 10 years, do you still want to be working side by side with this person? Could you take direction from them if you ultimately decide they should be the final say on something? Do you have the same exit strategy? Do you want to live in the same city as them? Do you want a small company or a big one? What kind of culture do you want your company to have? When are you both quitting your day jobs / consulting?
It may seem like discussing these things are premature when you're hacking in a garage, but the answers aren't nearly as important as the questions. You don't want to have a vision for selling a 50 person company to Google while your cofounder sees your startup as side income to his day job. And you definitely don't want to see your startup as an 80 hour/week gig while your cofounder sees it as a 10/hour week gig.
I follow Seth Godin's advice on partnership: 50/50 is a bad idea, period. Business requires decision-making, and someone should be the final say. If you wouldn't be okay deferring to your cofounder (even when he is wrong), maybe it's not the right cofounder. And ownership should be a factor determined by both time and money put in, not one or the other. Your agreement with your partner should stipulate how much time you'll be logging for the project, and ownership should be tied to actually "showing up".
http://danieltenner.com/posts/0005-starting-up-with-a-friend...
If you are at home... nobody is depending on you... It's easy to "drift". If somebody is there to say "Hey, did you finish X?" - that can be enough to get you to remember what you were doing, and get on it, without going off onto obscure feature land.
Whether you're hyper-motivated (and have a tendency to obsess about small things that don't matter) or under-motivated (and have a tendency to not really produce unless necessary), you'll benefit from a partner.
Just knowing someone else in the world loves your idea helps too. But again, I have to agree with the OP, make sure you are on the same page. Those "it sounds cool I'll chip in when I have time" people can be an absolute drain of your time and energy. (Those who want both money and an equity stake for one specific piece of the puzzle are the worst).
A co-founder has to be as committed as you are to derive the benefits.
People like to draw a distinction between funded and bootstrapped startups, including me (http://yieldthought.com/post/1156084359/single-vs-co-founder...)
The poster-child for single-founder startups is Patrick (patio11), although I don't know how many more times I can refer to him as a poster-child before he asks me to stop. Read everything he's written (http://www.kalzumeus.com/) if you're going to bootstrap something.
Another notable single founder is Gabriel Weinberg (epi0Bauqu): http://www.gabrielweinberg.com/blog/2010/01/will-single-foun...
http://searchyc.com/submissions/single+founder?sort=by_date
http://searchyc.com/submissions/solo+founder?sort=by_date
More important is a longer list of why startups fail:
Another big reason is that if I put a lot of work into a new design or a feature, I'm in the worst position to critique it. You need someone else who can provide objective feedback. Customers can do this to some extent, but it is very easy to dismiss their suggestions.
Related to that 2nd point, it is often tempting to say, "this is good enough" when you have to do all the work yourself. Having someone to push you to do better can really improve the quality of your output.
You can't contract a decent designer for $500 to launch a prototype?
You can't hire a good accountant for $50/session?
You won't muster up the strength to manage a remote programmer for $10/hour?
You'd rather give away 55% of your company?
then you probably shouldn't be starting a company.
If you're bootstrapping, it's helpful to have someone else to talk ideas over with, share the workload with and keep each other motivated and focused.
Some of would also be a factor of your personal skills and motivation and the scope of the project. It is certainly possible with the frameworks and hosting options we have today to get a project off the ground entirely on your own. But for larger things or building a "company" instead of a "lifestyle app", you'll generally end up needing multiple people to pull it off.
Something like 37signal's basecamp can be written by a single person. In fact, I think it was (at the beginning ..)
b. Two heads are better than one, partnering with someone has shown me that I don't have the god-like monopoly on good ideas that I once thought I did.
2. To share the work.