I went into a world where there was three item frames on a wall, which caused my 60 fps to go down to 1-3 fps. If the item frame is not rendered, there is no effect. In the item frames, I put some pretty powerful enchanted items (given with command blocks). However, this also happens with an item frame with nothing in it. This didn't happen in 14w03b.
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galaxy_2alex
Might be related, but this looks like a legitamate bug to me.
Basically: Placing Item Frames in the Chunks of spawn protection lags out the world.
If this is unique to 14w04a (try the world in 14w03c to compare), it would likely be a duplicate of MC-45458