Update: The tone of this post is a bit blunt. Maybe even rude. I've been meaning to update it, but since it's been almost 4 years and I haven't done so, I think it's safe to say I'm never going to. However, in the mean time, one or two people have mentioned that they found it useful, so rather than delete it, I'm just going to leave it up with my apologies for the tone.
One of the things I complained about in my last post was would-be company founders who are looking for nerds to build their product based on a specific idea or vision they've already created. Obviously, there's nothing wrong with hiring someone to build a product the way you want -- I build products for people all the time based on what they had in mind (and, I should add, I find this a highly rewarding experience). So what's the problem?
The problem happens not when you hire someone to build something a for you, but when you view your cofounder and/or CTO as someone who is building something for you. Your technical cofounder is not a contractor or regular employee; rather they are part of the core team responsible for the direction of the company. As such, they need to be invested in the company strategy (both literally, with stock, and emotionally) and their role is to help determine the company strategy and define the company's product.
You may think you've already defined the product, you just need someone to build it. If that's really the case, then get yourself a contractor -- ain't no shame in that! Unless your just doing something like building a simple e-commerce website as the storefront for your existing business, though, it's probably not that simple. Building new technology involves risks and tradeoffs, and you need someone who understands those risks and tradeoffs and how those risks and tradeoffs will impact the company strategy. That's where the CTO comes in.
Ideally, of course, all your employees should feel empowered to have some say over their domain area, but when founding a company, it's especially important to have a CTO who is invested. The reason is simple: most engineers are happy to build a product to spec, but a CTO who is invested will make sure the spec is both technically viable and makes sense for the business. Your CTO is, therefore, not just another employee: they are your partner in nurturing your product in all stages of development from conception to completion. This may seem counterintuitive if you already have a great, multi-million dollar idea, wireframes and so on, but it so happens that unless a technical person has looked it over and vetted it thoroughly (and probably changed it a lot), your idea is far from the great, multimillion dollar idea you thought it was. Worst case: it's not even viable. (Obviously, proper vetting from a technical person is not enough to make it a great, multimillion dollar idea, either, but that's another conversation). To put this another way, having your CTO invested in your product vision from the beginning removes significant risk from your business model because they can anticipate problems and see better solutions.
When I do contract work, there is always a technical person as part of the team that hired me. Whether that person is actually a CTO or not, they understand the requirements and know how my work is going to fit in with the business model, and they understand what tradeoffs are being made when it comes time to make a major decision. Without a person like that, who can make decisions with your business' best interests in mind, you will not be able to make the right technical decisions for your business.
In short, the job of a contractor is to build a product to spec on time and on budget. The job of the technical co-founder is to make sure the that technical decisions are made with business' best interests in mind. Both are useful people, but don't confuse the two.