Why is the wheel bearing grease leaking out of the dust cap?

I asked this question at FBBO before.
Nobody responded to say that they torqued them. All the respondents did the same as I do....we snug down the bearing nut, back it off to the next notch in the thin sheet metal cover and slide the cotter pin in.
Can you imagine though torquing them to 90 Ft lbs after MISreading the service manual?