Browser extensions suck.

flashsave.sh

#!/bin/bash

# Open a Youtube or other video in your browser, wait for it to load, leave the
# browser window open. Run script. Profit.
# May not work with Gnash &c.

lsof -u $(whoami) | grep Flash | awk '{sub(/[^0-9]+/, "", $4)
                                       sub(/\/tmp\//, "", $9)
                                       print "/proc/"$2"/fd/"$4, $9".flv"}' | xargs -rn 2 cp -n