There used to be a range of 24 blocks around players where hostile mobs could not spawn. This rule is still described in the wiki.
However I have on multiple occasions seen skeletons, creepers, spiders and zombies spawn within less than that. The latest creeper was at 5-6 blocks distance right when i'm looking in that direction.
Additionally they instead of immediately despawning once player is 128 blocks away, they remain frozen and are saved in the chunk. This is evident when you return to the location by day and skeletons/zombies start burning. This also applies to vertical distance. In 1.6 when I was 130+ blocks above ground i had no loaded entities, now they remain loaded and applied to mob caps.
MC-40959
Spawn/despawn radius rules broken
Resolved
Duplicate
1
Yordan Gigov
(Unassigned)
Unconfirmed
Minecraft 1.7.2
Retrieved
Just FYI, the wiki is NOT a validation source, while it may be occasionally referenced for ease of providing information, it is information put together by players not Mojang.
The report you have submitted is working as intended, mechanics of the game may change between updates. Things such as biomes, redstone, villagers and animals, may not work the same in current versions.
We strongly recommend that you don’t run 1.7.x on an existing world if you don’t want to run into chunk border issues.
World structures such as Nether Fortresses do not transition to 1.7 from 1.6, but loading these areas (and standing in them) in the new pre-release 1.6.4 and then going to 1.7.x should fix this.
For more information see: Version History