For anyone wondering, I just did this on OS X to adjust the throttle overnight:

  > crontab -l
  0  1 * * * sed -E -i .bak 's/net_throttle="[0-9]+"/net_throttle="100"/' /Library/Backblaze/bzdata/bzinfo.xml
  0 10 * * * sed -E -i .bak 's/net_throttle="[0-9]+"/net_throttle="40"/'  /Library/Backblaze/bzdata/bzinfo.xml