Let's say I run into you in the grocery store. You are pleased to see me and say hi effusively. But I don't recognize you. I'm quickly scanning my memory -- should I be remembering this person? "Do I know you? (Should I be remembering you?" At this point you will take pity on me and tell me how we met, where we interacted.

I don't say "Do you know me?" because clearly you do.

Let's say I run into you in the grocery store. You are pleased to see me and say hi effusively. But I don't recognize you. I'm quickly scanning my memory -- should I be remembering this person? "Do I know you? (Should I be remembering you?") At this point you will take pity on me and tell me how we met, where we interacted.

I don't say "Do you know me?" because clearly you do.