One interesting phenomenon with The Wall on Facebook is that you end up watching a lot of conversations between your friends. Since the activity stream shows messages between two friends, it feels like you are a fly on The Wall.
It isn’t like it feels dirty or anything, the wall is a very public place, and everyone knows that. I do feel like the wall is a bit of a weird place though. The UI is always strange when someone writes on my wall. Instead of putting the darn message in my Facebook Mail inbox (or what I really want… send it to my email address so I can just READ IT ;) I get a notification, which I ignore a lot as they are normally to do with someone wanting me to pat a monkey, or get a beer. The apps that make me install them just to GET the thing that was sent to me really bug me too, but that is another matter.