Found out recently that the default Bluetooth Connection Pin for all Sphero's to connect to a computer's Bluetooth is: 1234. Tested on V1 and V2 Sphero versions.
When you initially make the connection from the Sphero to the computer's bluetooth, you can choose NO PAIRING CODE, similiar to the Wii connection. When you try to connect in ARC using the Sphero connection button, then the OS will ask (with a balloon pop-up) for the pairing code, which is 1234. Enjoy