In his assessment of the risks involved, the author didn't mention the possibility that purchasing coins from the mint could be considered a cash advance, which is like taking a 15% APY loan with interest accruing immediately after you take the advance.

EDIT: Also, looks like the mint has caught on to this guy (http://catalog.usmint.gov/webapp/wcs/stores/servlet/ProductD...):

The immediate bank deposit of $1 coins ordered through this Program does not result in their introduction into circulation and, therefore, does not comply with the intended purpose of the Program.

Not sure that's legally binding, but it's at least a dishonest thing to do.