The software that ran the "core business" of the company. The CEO and I decided to not hire an off-the-shelf solution, which would do everything that we wanted to do, but would put our data into the vendor's hands and we thought that it was not worth the risk. After all, we are gonna be huge and our data is our oil!

A few years later, our internal version of this software was crappy and our data was still not something that we could monetize. In the future, I'd refrain from being too cautious at the beginning when you are facing bigger risks that may not be sexy, but are very dangerous.