Minecraft 15w34a, Minecraft 15w34b, Minecraft 15w34c, Minecraft 15w34d, Minecraft 15w39c
OS: OSX Yosemite 10.10.2
When you have a scoreboard that tracks whenever a particular item is dropped, it both increments for when you drop that item (as expected) but also for when you use the /give command to give the player that item.
/scoreboard objectives add EggDrop stat.drop.minecraft:spawn_egg
Then upon doing...
/give @p spawn_egg
... the 'EggDrop' scoreboard increments by 1.
I have tested this with a few other specific items and the same problem occurs.
However for dropping items in general, using stat.drop works as intended, so it's just for dropping specific items. I'm also aware that this same problem happened with the 'stat.drop' when that stat was first released, so I expect it's the same kind of problem here.
MC-86951 Drop item scoreboard objective increases with /give