Open terminal and type:

$ sudo \[installer location\]/Contents/Resources/createinstallmedia
--volume \[usb location\] --applicationpath \[installer location\] --nointeraction

or, mine like this:

sudo ~/Desktop/Install OS X Yosemite.app/Contents/Resources/createinstallmedia \
--volume /Volumes/Untitled/ \
--applicationpath ~/Desktop/Install OS X Yosemite.app/ --nointeraction

and if its right, you will see the % of progress and status

Image from arstechnica