Evan Schuman's StorefrontBacktalk

That’s a reasonable argument. But it’s still an argument a retailer would have to be making in court, which isn’t a place any retailer wants Wi-Fi to connect it to.

For Randazza’s part, he clearly doesn’t believe any of the defendants he’s fingered are actually innocent victims of Wi-Fi theft. But let’s say one of those IP addresses did belong to a Starbucks. What then?

“We tested this,” he said. “Starbucks could block or throttle this kind of activity. You’d have to sit for three hours to allow one movie to upload.”

And no one has ever sat in a Starbucks for three hours?

It’s actually riskier than that. As the Massachusetts lawsuit spells out, BitTorrent doesn’t require movie thieves to sit for hours while a movie downloads. A “torrent” involves breaking the movie up into pieces, which then can be downloaded from many different computers—not even necessarily all at once.

So if a would-be movie thief walks through a mall from one free Wi-Fi-enabled retailer to the next, using an iPhone or iPad to slurp down a few pieces of a stolen movie at each store, every one of those stores’ IP addresses could conceivably show up on the list of thieves. And if the Wi-Fi negligence theory holds up in court, some overly aggressive plaintiff’s lawyer could list all those retailers as defendants in a negligence lawsuit.

None of this spells doom for in-store customer Wi-Fi, at least not yet. Both the Wi-Fi negligence legal theory and the idea that Wi-Fi-offering retailers aren’t covered by the DMCA have yet to be tested. And there are bigger problems with letting customers use the in-store Wi-Fi for whatever they please—there’s really no limit to how much bandwidth some customers would happily soak up, in ways that don’t have anything to do with moving merchandise.

But it’s probably not to early to start thinking about how you might keep an eye on that customer Wi-Fi traffic, or even filter out connections that don’t seem to have anything to do with making actual customers happy. That way, even if you get dragged into court, at least you can say you tried.