Once you've been here long enough you realize that your wall will fill up even by those who are not following you or being followed BY you. The notification lets them know there is someone new to talk to, but they could easily comment on your wall without following or being followed. So if they wanted to talk to you they would either way.
I often follow people who post reviews I like, we have something in common, we've chatted around the forums etc. I leave comments here or there but there are a few who we can leave multiple posts a day!