It is is definitely NOT, "oh well I'd better just go ahead and execute and get a product out and get customers all by myself, and then talk to Joe and cut him in for less equity, because I want to set myself up for needing only a $17MM acquisition to make $5MM."
Now none of me or Joe's Next Great Ideas have ever panned out, so maybe we're doing it wrong. But I still don't think trying to optimize for a payout when considering co-founders is doing it right, either.
At the other extreme, some founders' personalities are such that they almost have no choice but to build it completely on their own - a "lone ranger", as a investor I once knew put it. My favorite example of this is Felix Dennis, founder of Dennis Publishing (which publishes Maxim, and many other magazines).
(That's not to say lone rangers build their company alone; if that's ever been done, I don't know about it! But the additional key people are employees, not founders, and may not even get equity.)
He's not advocating single founder startups, stop the pointless arguments.
The most interesting part:
"if you raise a third round (or even a fourth), that pushes the needed sale price up further. If you're at 10% founder share with two co-founders, you'd need a $100M exit to get your $5M."
It's all about creating value.
Anyhow, this combined with his post on the startup career path (http://www.gabrielweinberg.com/blog/2010/11/are-you-in-a-sta...) are two of the very best pieces of advice you're going to get IMO. @yegg is the man and his posts always deliver.
Personally, I'd prefer to have a co-founder, but only one.
1. Single Founder
Have you ever noticed how few successful startups were founded by just one person? Even companies you think of as having one founder, like Oracle, usually turn out to have more. It seems unlikely this is a coincidence.
What's wrong with having one founder? To start with, it's a vote of no confidence. It probably means the founder couldn't talk any of his friends into starting the company with him. That's pretty alarming, because his friends are the ones who know him best.
But even if the founder's friends were all wrong and the company is a good bet, he's still at a disadvantage. Starting a startup is too hard for one person. Even if you could do all the work yourself, you need colleagues to brainstorm with, to talk you out of stupid decisions, and to cheer you up when things go wrong.
The last one might be the most important. The low points in a startup are so low that few could bear them alone. When you have multiple founders, esprit de corps binds them together in a way that seems to violate conservation laws. Each thinks "I can't let my friends down." This is one of the most powerful forces in human nature, and it's missing when there's just one founder.
Can't think of any truly one man operations off the top of my head, although Zuckerberg was almost running the entire show at Facebook.
I've bootstrapped a business to significant traction as a single founder. I don't recommend it. It's possible, but morally exhaustive.
edit: minor edit for correctness.