There appeared an interesting analysis by Daniel Amitay of most common Iphone passcodes http://amitay.us/blog/files/most_common_iphone_passcodes.php
His Iphone App analyzed passcodes of the users. What he discovered wasn't surprising. Most common passcodes use easy combinations such as 1111, 1234, 0000 or users' birthdates. I would bet that similar patterns apply to SecurID passcodes many of which are also just 4 digits.
204,508 recorded passcodes, the top ten most common were: