Lost caps to thumb drives, is this a big deal if USB end is exposed?
 

This where those turtleing ones have an advantage, but I like the regular ones, they are easier to insert into a usb port, but I lost the cap on one the other day, will it harm the thumb drive if the usb part is not covered by a cap? I carry them on my key chain.

Only insofar as you allow dirt, lint, grit and other foreign matter to hide away in the USB port. You could always cover it over with a piece of Scotch tape if you're really worried. Remove and replace, as needed.

It really depends more on how clean you and your clothes are. A kid, for example, would probably have mud caked in it after a day. A businessman in a suit would have no more threat the lint from a coat pocket. If your keys are stored in a purse (or that camera bag), then it could be perfectly fine, and there's absolutely nothing to worry about.

My drives sit open almost 24/7, because they never move much out of the office.