None of the sharks made an offer to invest except for Kevin O'Leary , who Siminoff turned down.

The investors on ABC's "Shark Tank" had a chance to be early backers of the business — Ring CEO Jamie Siminoff appeared in a 2013 episode seeking a $700,000 investment in exchange for 10 percent of his company, then called Doorbot. But they missed out.

While you might imagine the sharks would regret missing the chance to invest, Mark Cuban says he stands by his choice not to make an offer.

"I would pass on Doorbot again if given the chance," Cuban writes on LinkedIn, in response to another user's post.

That's because Cuban had concerns about how much capital the business would need in order to grow.

"While Jamie did an amazing job turning Doorbot into Ring, I have a fundamental aversion to companies that require raising hundreds of millions of dollars to do less [than that] in revenues," he explains.

"That's not a knock on Ring. [Siminoff] was on a mission and he is achieving it," Cuban continues. "He earned every dollar. It wasn't easy for him. This is about what I look for, and Doorbot didn't fit."

O'Leary too says he saw promise in Siminoff, but had problems investing in the business at its then early stage.

"I liked [Siminoff] a lot. I thought he was a great sales guy, but at that time his valuation was insane," O'Leary tells CNBC Make It. Just like Cuban, O'Leary says he made the right choice.

"I never think about it a second time, I really don't," O'Leary says. "I feel that the road is always going forward. You can't go looking back — you can't second guess yourself. You have to do what you think is right in the moment.... For that time, I made the correct decision."

Both O'Leary and Cuban say they're happy for Siminoff, and hope he inspires future generations to be ambitious and entrepreneurial.

Cuban tweeted, "Congrats Jamie !!! Always a beautiful thing when an entrepreneur succeeds. Way to ring the Amazon bell!"

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