knockthrough:~ chris$ sudo dd if=~/Downloads/2015-05-05-raspbian-wheezy.img of=/dev/rdisk1s1 bs=1M
Password:
dd: bs: illegal numeric value
fixed simply with
knockthrough:~ chris$ sudo dd if=~/Downloads/2015-05-05-raspbian-wheezy.img of=/dev/rdisk1s1 bs=1m
knockthrough:~ chris$