A friend in Texas claims they recently bought one at Wal-Mart. I don't know anything about how these work but that can't be true ... right?

Yes. I've also seen them sold on other online retailers, including Amazon. They're pre-infected boxes, acting as a voluntary network implant under the guise of being a sneaky way to consume otherwise-paid-for content.

There are plenty of people selling IPTV access on g2g, few bucks for a month, all TV channels from entire world. I am not sure if it is profitable to let such piracy boxes work forever, even with them being used as residential proxy, but I also don't know how low you can go if you skip middlemen.

It's absolutely true, these are sold all over the place