Pronounmonia

Do you remember those English lessons most of us endured in school about pronouns?
We learned about possessive pronouns, personal pronouns, and all of their cousins and family members. Well, apparently it didn't take or to put it another way, those lessons kind of went in one ear and out the other!

If you do not believe me try looking at some of the posts on social sites. Soon you realize that either folks do not proofread what they write or that they do not know which or what is correct. Sometimes you see nicely prepared signs or sayings with incorrect pronouns posted by your friends.
Do you ever wonder why they would post them if they know they are not grammatically correct? Am I the only one who wonders?