A long time ago on mainframes. IBM 3083's and VAX's. I was running analysis on some waveform data, took probably about 20 reels of mag tape. Fucking marine seismic data. I sent the big deck of cards down to the floor on a Friday. 1st thing Monday, I had to go the VP's office. He explained that Monday morning, the fucking job was still running. Turns out, instead of sampling the data every 4ms, I accidentally sampled it every 2ms. Back then, you didn't own your mainframes, IBM leased it to you. The VP explained that I cost the company anywhere from $40-60k. Nice guy actually. Texas engineer, cowboy boots and a suit. He politely asked me, "Son, you probably won't be making this mistake again, will you?" I stuck around for another couple of years. Goddamn it took an army to process data back then.