I'm not someone who participated in the MyPoints-Tupperware offer, but all I have to say is this:

Hey, this is capitalism. It's up to the business to make sure they can compete in the marketplace. If they have a $5 minimum on gift certificates, they should have some sort of (very, very simple) safeguard in place to make sure you can't buy one for less than $5. But they don't. They shouldn't lash out at the consumer -- that's bad business; they'll just end up losing customers. They should close the loophole and continue from there.

I can't blame consumers taking advantage of a business's stupidity when businesses take advantage of consumers' stupidity all the time. It's a two-way street of manipulation.