(On my realm) i think IF got deserted the minute they put an AH into SW(Can't remember if that was end of Vanilla or TBC?) Maybe some still used IF for Ah action up until Cata, but not many. When Cata and the zone portals came IF and all other ally faction cities could have been taken out of the game and my server wouldn't have recognized it for quite a while At least with the CRZ IF is now crowded again. Thats really nice imo
And even though i like the memories from back then, i have to admit that i always kinda prefered SW. We had guild meetings in the castle and did a lot of RPing there in Vanilla.
side note: duelling in front of the IF gates was awesome. Even more awesome was climbing the hills with a bunch of friends and jump down from those gates. Seeing every duellist stop in the middle of their duells when 10+ people fall out of the sky was amazing^^