Before One Tamriel, players generally had contact on daily basis only with players from same faction. Sure they could have characters in different factions or be in multi faction guilds but generally the playerbase they had contact with was 1/3 of total playerbase.
After One Tamriel and removing faction restriction, in general the amount of people an average player have contact with tripled. In consequence amount of social interactions also increased.
That's why the limit of 100 players on friend list (and possibly ignore list too) should have been increased at least to 200 or even more. Why it didn't happen?