Scammers can represent themselves as collection agents for your utility company, loan officers at your bank, or administrators of some kind of sweepstakes. That appeals to our innate greed, of course: we’re happy to send huge amounts of cash in exchange for even more cash.
Greendot isn’t the problem here, and neither is the Moneypak. The only problem with that product is that it makes it so easy and simple to transfer money quickly and without knowing much information about the person you’re sending it to. That can be a positive thing in some contexts, but in this context is a bad one.