CanPickUpLoot:true doesn't work

CanPickUpLoot is a byte and to be set to 0 / 1
Nevermind.

But please provide the exact command you've used to spawn the mobs.

/summon Zombie ~ ~1 ~ {CustomName:Clone,CustomNameVisible:1,Attributes:[{Name:generic.movementSpeed,Base:0.01}],CanPickupLoot:true,isBaby:1}

And the stripped version (doesn't work either :s):
/summon Zombie ~ ~1 ~ {CanPickupLoot:true}

Can confirm. Doesn't work with /summon Zombie ~ ~ ~ {CanPickUpLoot:true,} nor {CanPickUpLoot:1,}

The tag must have the tag-type of byte labeled:

/summon Zombie ~ ~1 ~ {CanPickUpLoot:1b}

You must also ensure the gamerule "mobGriefing" is set to true.

Great! It works with your command. Thanks.

Doesn't work anymore in 1.8.8

@WesselH, It does, ensure the mobGriefing gamerule is set to true.