I was once in charge of running an A/B test at my work. Part of the test involved driving people to a new site using AdWords. After the test was complete, I f

I was once in charge of running an A/B test at my work. Part of the test involved driving people to a new site using AdWords. After the test was complete, I forgot to turn off the Adwords. (Such a silly mistake...) Nobody notices until our bill arrives from Google, and it's substantially higher than normal. When my coworker came to ask me about it, "are these your campaigns?!?" I just sank in my chair. I think it cost the company $30k. I suppose it's not that much money in the grand scheme of things, but I felt very bad.