How is this not a problem in practice? So much write I/O into a temp directory is slow and error-prone, and also you can't guarantee cleanup in case the process quits abnormally. And it's not like the average user will be fond of downloading and unzipping things manually. I know I absolutely loathe programs that self-extract files on a regular basis, and judging from the pains people went through to avoid it here I don't think I'm alone.