What's up with the smiley faces

This might be old news to all of you (including me) but over the past few days I've really started to wonder why so many wordpress.com blogs seem to have the stat trackers with the 'smiley faces' ? It is to cheer up the mood of the reader? Or perhaps is it a smiley face just for fun... but now since so many blogs have the smiley faces, I think my blog needs one. So I guess I'll have to get my self a smiley face as well.
Update: The smiley face is now on my blog as well !