Aren't those just files used for indexing, storing icon data and removing things from the Trash? I've seen Mac stuff like .trashes and what not whenever I connect a drive or card to a PC. I predominantly use a Mac and on the Mac they are invisible and seem to only show up on a Win, Linux or similar computer's filesystem where they're set to show hidden files. Kind of like those little irritating thumbs.db files that Windows creates.
You can try installing
Superdocker or another application that allows you to see files the OS usually hides and delete them. Unfortunately they will likely come back as they are a part of how OSX (at least 10.5/10.6) work, if I'm not mistaken.
Here's how you show the files using Superdocker. Show hidden files.

Here are the files he's talking about, MCL. This is from one of my drives. The tilde ~ character that you see, Stinktank, in the MPC is usually there because the file name contains too many characters. On your Mac OS or Windows these files will have longer names, likely.

I've never seen them on my MPC CF though.