What constitutes a startup mistake?

I don't think the point of this article is quite warranted. What looks to you like something you could only have figured out in hindsight may well look obvious to someone more experienced. Let's take a couple of examples:

Yes, getting the founding teams right is hard. I agree there are issues with single founders and there are plenty of issues in quickly-assembled founding teams. No, co-founders who’ve known each other for a decade are not a recipe for success either. I’m not sure one can label the general challenges people have with founding team formation a mistake. How much of that is really in the control of the lead founder at the time of making a founding team formation decision?

Fights between founders can definitely be avoided. In my case, if I'd read the article which I later wrote on the topic (http://danieltenner.com/posts/0005-starting-up-with-a-friend...) it would have saved me a very costly mistake. There are many ways for people to fall out, but with enough experience, I would think that a savvy entrepreneur should be able to render them much less likely and much less harmful.

Another example of determination that’s typically made ex-post. Just think about all the startups that got caught by the crash in 2008 with too little cash on hand. Had there been no crash, they may have done just fine. Should they be blamed for not seeing the crash? In good times, some of the companies whose CEOs always want plenty of money in the bank are blamed for raising too much money. In 2008 they were geniuses.

That's also not a fair comment. As far as I understand it, raising large amounts of money isn't a "here's a bunch of money, do what you want with it" kind of deal. If you raise $10m, you're damn well expected to put that $10m to work in the near future. I'd be surprised if any VC let you keep that money hanging around for more than 1-2 years tops (except, of course, if a recession suddenly hits). Certainly, during the good times, they'll want you to spend it - on growth, mainly, I believe.

So raising too much money is fairly predictable ahead of time: if you don't have solid, worthwhile plans for how you'll spend that money, raising too much money will force you to make up plans for how to spend it, and hire people to implement those plans. Hiring more people than you need will slow you down, and potentially cripple you, so that you wouldn't be able to implement the thing that you did need to focus on (and which perhaps only required 1/10th of the people that you hired).

So, on the whole, it seems to me that this article makes an interesting but flawed point. Experience turns hindsight into foresight.

They are all issues that distract you from your appointed goal, to build a company from scratch. You start spending your time getting back on track and not going forward and your are done for.