I still remember one day in a great game of Civ 2 on a larger map, I was doing well, had just spent a LOT of time designing some new ships and micromanaging my economy over the course of several turns.  I went to the diplomacy screen to demand the surrender of a minor race.  I screwed up and accidentally surrendered to them.  About 2 hours worth of work, just gone, because there was nothing that made it clear how badly I had screwed up.  An "Are you sure you want to surrender?" would have made me open my eyes and realized I had clicked in the wrong column. 

I will be the first to admit, it was a stupid (and hopefully amusing) mistake, but at the time it was a very frustrating loss of time involved, because I simply didn't realize that my HUGE empire was surrendering to the minor race of squirrels.  With one planet. 

I guess I just really wanted their nuts, or maybe I just wanted an excuse to be a little squirreley, or something.... but seriously, not worth it