The mere action of 1 bumblebee landing on the tassels realeases a cloud of pollen sufficent to pollinate all silks in a ear...
Corn is wind pollinated primarily, I walk through my corn when it's tasseling stiring up a cloud of pollen. bee's would be a good thing, and as Tatws stated...No detremental effects from these marvelous helpers.
Also, If you plant your corn in blocks (and you should be) pollination will be enhanced..always plant at least 4 rows, even if they are short rows...

A much worse thing that can happen is a week of DOWN POURS, or watering overhead while the plants are shedding pollen