One of the greatest happenings on the net before the new millennium and after the arrival of Mosaic, was the arrival of the ICQ network.
ICQ happened to be the first widespread buddy list/instant messaging (IM) software for the Internet, and for several years ICQ was the dominant tool. Ever since ICQ got competition (by AIM, MSN messenger, Jabber, Yahoo messenger...) I thought there will soon be a buddy list protocol, so that users can choose the IM client they like, yet keep in touch with friends who have other clients. But for some reason the IM world doesn't seem to want standardization.