It's interesting that many comments posted in this thread assume that just because they don't have 100 friends that there is no way ANYONE would have 100 friends. We must remember that our own personal situation is not necessarily reflective of others. Furthermore, there are those outgoing individuals and people in public arenas (for example, Jim Sterling) that could easily have a need for such a large friend's list because they have a large following and need to maintain social links in order to maintain their own publicity. While I myself don't have anywhere near as many people to put on a friend's list, I do know that not everyone in gaming is a unsociable recluse or a shy introvert. Such people could easily push the limits of the 100 limit friend's list.
Another thing is that the concept of "friend" on the Internet has a very, very loose meaning compared to how the concept is regarded in real-life social interactions. Often on the Internet, "interesting person", "casual acquaintance", or "momentary associate" is enough to garner "friendship" status. Often, just someone you played a game with once and had a lot of fun playing with them is enough to obtain "friend" status. However, in real-life, obtaining the status of "friend" generally takes a long-term social interaction in which there is a build-up of trust, sharing, companionship, and emotional support. There's much more weight in the concept of friend in real-life, and because of the time and effort required, most people are likely to not have 100 real-life friends. But, because on the Internet, friendship has such loose regard and restriction, it is not usual for someone to develop a list of 100+ "friends", even though they only associate with those people briefly, compared to the much longer term basis of real-life friendships. Furthermore, Internet friendships tend to be brief, but not everyone makes the effort to prune their "friend's" list unless they absolutely have to (although, this could be a rationale for a limited size "friend's" list, to force pruning at SOME point); so, it's not unusual to have a grown list of dormant "friends".
I guess ultimately where I am going with all this is that people shouldn't assume that just because they themselves do not have a large "friend's" list, they shouldn't assume that it is not true of others. Public figures and high extroverted persons (yes, they do exist even in gaming) can easily develop large "friend's" lists. Further, the loose regard of the concept of friendship on the Internet can easily lead to extremely large "friend's" lists, even if those "friend's" are only a very brief association, because people quickly associate someone as "friend" and don't always prune their lists of dormant "friends".
Of course, the ultimate question, as several have voiced, is whether there is a real technical reason that the "friend's" list has to be of finite extent. If there is a technical reason, such as storage requirements, then it is reasonable that there should be a fixed size; however, the limit should be in proper proportion to the capacity of current technology, not technology of 10-15 years ago when a limit of 100 made more sense for reasons of technical limitations.
