This has nothing to do with the fact that it's a flash device. It has to do with the block size of the filesystem you're using and no, it doesn't write 4MB or 8MB at a time....the default block size for FAT32 is 4Kb.
sounds like someones done a bit of googling.
Regardless, I've had personal experience with clips ending early as the capacity is nearly filled. So I take that into account from now on.
