I have never completely forgotten someone that I dated. I do feel like this would be hard to do, unless you either date a tremendous amount of people or are aggressively rude. What I have done is completely forgotten about people that I used to be fringe friends with, or people that I basically grew up with, going to the same classes for upwards of 10 years. I know this borders on me sounding like a straight-up jerk, but I’m sure I also act as the forgotten in other’s minds also, so it’s whatevs. Like, I went to a party back in my hometown two years after I graduated high school, and I ended up talking to this girl who I knew that I was supposed to know and I couldn’t remember her name or anything about her. In writing this out I’m realizing, rather alarmingly, that this may be more a symptom of a memory issue than anything else.