I've noticed resources spiking on a vanilla 1.7.4 server ever since the 1.7.4 update. I've had to visit many peoples bases and check entity counts and X-ray to find the problem:
What I notice is heavily used areas that aren't well lit underground are becoming a big issue. Chicken Jockeys will randomly spawn, and when the baby despawns it will leave the chicken underground laying eggs.
This leads to the other random zombie spawns to pick up the eggs (In hard mode about 50% of them) and they won't despawn.
So not only do I have tons of underground chickens to deal with, but tons of underground zombies holding eggs.
I consider this an unintended consequence of the new chicken jockeys, and suggest they either despawn with the zombies and not lay eggs, or have some configurable option to turn them off.