I know the names of the people who post a lot but most people I just associate their user names with their dogs name, if that makes any sence. Ok for example, when I take my girls to the park for a walk I'm like "Oh that's Gucci's mom" and I totally forgot or don't know the owners name because usually when I see another person with a Yorkie or a cute dog and say "Hi" I usually just ask what their dogs name is instead of the owners name and they do the same (I guess it's just out of habit, which i guess is kinda wierd).
It actually happened to me today with a girl I always see at the park and we finally kinda laughed and asked what each others name is because we were just so caught up with eachothers dogs.