They've started to leak around the rim and crust over more recently.
I had never noticed this phenomena until last year, but now
it seems that 1 in 3 milk jug has a slippery, smelly, 
crusty, and overall disgusting patch of possibly-rotten milk
on it, often with dirt stained in, just for good measure.

Here's my question: If milk, a relatively thick liquid, is
getting out of the seal, then what the hell could be getting
in?