Gary,
I have talked to David about this. I believe if you check the conference call recordings, he discusses this at the end of one of the phonecalls. It is a substantial amount of money–the monthly value of the lease (say $900) times 12 (months) times the number of years you have the leasehold for (say 5 years). So you would secure it with $900*12*5 = $54000. I have yet to do it myself. According to him, he simply tells them that this is how we do business and we need to protect ourselves. He said he has never gotten flack over it. Find the phonecall (around end of Sept/early Oct of this year) for more information.