Well, I'm not a Mac user, so I can't really test this, but one would think that it shouldn't be able to work this way, as a file has to be marked as executable (i.e., chmod 755) in order to run. Images don't need to have the executable bit set to display, so I question whether this tidbit is true. /. is not the best place to get accurate information, but can often point you to a place to look :-)
True. On the other hand, you can gzip it with the executable bit, and when it's unzipped it'll be ready to roll.