A few months ago I started a company with a person (let's call him X) who was recommended by a good friend. X talked very passionately about the domain. I'm a tech guy and I have very little exposure to the domain. I thought that with X's domain knowledge and with my tech expertise we could form a synergy that would drive the company big.

We brainstormed a few ideas and decided to quickly build prototypes and iterate over our ideas. But when it came to execution, X just wouldn't do anything - wouldn't talk to clients, wouldn't talk to investors, wouldn't discuss strategy with me, wouldn't come up with a product plan, wouldn't discuss features, wouldn't do anything at all. X always made excuses of being sick or having family emergencies.

I had to align X's energy into building the company several times. After a point I realised that X was not motivated in running the company at all. When I threatened him with the idea of leaving the company, he didn't confront me. Rather, he accepted that he was not motivated and he came up with an excuse of why he wasn't able to perform.

Last month we shut down the company. Now I'm back to searching for jobs again. I'd like to know if it's okay to speak about your co-founder's incompetence to a prospective employer? I'd like to be honest with my prospective employer. I'm also willing to accept my mistake of not being able to judge a person's competency. But then again I also know that badmouthing can get me in trouble.

How do I position myself when someone asks me: "why did you close your previous company?"

PS: I've parted ways with all my previous employers on an extremely good note.