The concern is not with the USB connector. It is isolated from the circuit board. Dust and light moisture can easily be blown out.
The real problem is with that microSD slot which exposes the circuit board. Mine is covered with tape but a plug should have been supplied.
Actually, some heavy exercisers have reported concerns or issues with sweat and the USB port.
I agree as to a card slot concern. A reason I keep a card in the card slot, even if I’m not using the card.
If you only want to fill the card slot and don’t care about the memory, here’s a 2gb card at $3.75 shipped. Nicer looking than tape, it seems to me.
And by the way: frys.com has Polaroid 8 and 16GB microSD cards on sale right now at $10 and $18, after rebate (with shipping at only $2). Nice prices!