Seems like I've read that various and sundry scurrilous characters have hired ex-soviet "nuclear guys".
If you were one of those guys, what do you think your "half life" would be the day after OBL discovered that the "suitcase" you advised him to purchase -- instead of going "Boom!", went "Sproing!" as a smirking clown puppet popped out the top?
Do you think its even remotely possible that the people who managed to coordinate the 9/11 attacks have taken some of these details into consideration, and taken steps to ensure that they've got a modicum of possibilty of carrying out what they intend?