"One or more partitions are busy on /dev/sd*" what to do?
I believe it's being automounted. You can't format a mounted partition.
In Disk Utility click on "unmount" and then click "format".
"safely remove" will not let you format the USB stick, because it may actually unmount the drive and then tell the interface on the USB stick to power down. After selecting this option you can normally do nothing with the device until it is removed and inserted again (which will cause it to automount again...)
