There are many, MANY individuals out there who will purchase the Premium just for the merch discount.
Many of those will actually buy the pass and never intend to spend one day at the parks.
There are a few who will actually go into WoD and drop several thousands of dollars WEEKLY, with shopping assistants, and then apply their discount.
They then go back and sell everything they purchased, if it wasn't already sold, online for the same up-charge as their discount.
20% discount is a 20% profit / business to them.
This happens daily. This happens throughout the property. This is a big issue.
To add to this... want to know one of the reasons why all the Party Merchandise, Limited merchandise, etc disappears way before you make it to the party or special event? You can thank these same individuals. They know their limits, they know how to work around the loopholes, and will literally buy passes for every member of their 'families' and max-out the limited amounts per individual. There was ZERO Halloween merch after about Oct 15 this year... and boy did that suck. Even used a local supplier for shirts for MVMCP to avoid this happening again, but pins were long gone before the last 5+ parties.
It is not difficult to track these people down (they have actually HANDED CM's their business cards in the merch locations, while others will actually brag out loud in front of other guests about their intentions and then plug their websites).
The problem is linking them to the online transaction. Even if Disney is able to find the person and link the fraud to the premium pass, the most they would do is cancel the pass. In extreme cases, there are several sources out there trying to eliminate the fraud, but it is a big issue.
The common guest is catching on as well. These same scenarios are expanding at an increasing rate.