I no longer update this.

Smuggled:

Easter Bunny Trading Card
Twree Trading Card
Jet Trading Card
Vibue Trading Card (2)
Glowing Melted Egg (2)
Enchanted Ninja Knutt Plushie (2)
Checkered Costume (3)
Camouflage Costume
Female Certificate (2)
Male Certificate
Brown DNA
Pearl with a Hat (6)
Smuggler Plushie (9)

Seen:

Easter Bunny Trading Card
Flamed Trading Card
Jet Trading Card (3)
Angel Costume (3)
Glowing Hairy Egg (3)
Glowing Melted Egg
Checkered Costume (4)
Old Costume
Enchanted Ninja Knutt Plushie (2)
Vibue Trading Card
Shadow Trading Card
Male Certificate
Female Certificate (2)
Brown DNA (6)
Pearl with a Hat (7)
Smuggler Plushie (13)

Ignoring Pearls and Plushies, I've Smuggled 17 items out of a total of 47 seen. My rate of Smuggling is therefore 36.17%.