Some people (like myself) get major fps drops in areas with a lot of item frames. I made a simple mod that changes how item frames are rendered depending on how far away you are. This is really useful on servers that have economy / shop plugins that uses item frames. This mod works with Optifine as well.
It depends on your system, but on mine when I have a lot of them with items in them it gets a lot laggier when I look in the direction of them. It presume it's from adding a lot of extra stuff to render when you have 200+ item frames with stuff in them.
Btw I got my problem fixed. It was just something with optifine, and I think the 1.4 update or something added a fog to entities. Great mod! And I can finally start sprinting in spawn with those item frames..... Thanks for the mod!