If I understood this article right, the process works like this (correct me if I'm wrong):

Bullion Banks hold the metals.  They act as the middleman, providing the link between the mining operations and the industries which consume those metals.  Metal leasing is when metals are "leased" from a Central Bank to these Bullion Banks.  The fraud comes in the fact that you can't lease metals. 

How in the world can you "lease" something that gets consumed?  Its like saying you can lease firewood.  The truth is that these are metal sales, and because they aren't defined as sales, it doesn't appear in their books.  The article also points out that these are done with 0.5%-1% interest with no securities, which raises red flags.  These same central banks (through Mae and Mac) issue home loans that have securities that are around 6-7%.  Why would you charge less interest for something you have no securities for?

The motivation behind the article does make me a bit skeptical.  Whenever I hear something tell me to buy something (in this case its precious metals), I suspect something is up.  It doesn't mean the article is wrong, just that perhaps theres something not being included.