Really, this has been debunked? If I can get something at a cheaper cost (whether by stealing or some legal mechanism) then I won't get it from another mechanism.
For example, I used to rent seasons of shows on DVD (and on some rare occassion bought boxed sets from Costco). Haven't done that in years. Just wait for Netflix. Now Netflix isn't stealing, BUT if bit torrents just became completely legal right now, I'd probably cancel my Netflix subscription.
I'm not saying that every "stolen" copy is a lost sale, but it does sound like the potential qualifier is pretty accurate.
I think the reason to the strong reaction against the term "potential lost sale" is because this is often used by the *IAA to then massively overstate the losses from piracy. It has the potential to be a lost sale, but the question is how likely was that person to buy the product if an illegal version had not existed?
For example, without piracy, many of my friends (young twenties/teens, so we grew up with piracy) wouldn't have the same taste in music or movies without piracy because we simply would have never found a lot of the stuff we now greatly enjoy. The chances they would have purchased a good deal of their favorite media without piracy existing are utterly minuscule, and to say it's a possible lost sale somewhat glosses over the details, although it is technically correct. That's not to say all piracy would never be purchased, but I think that's the case for a lot of piracy. This is just my personal opinion, but I believe I've seen more statistics that point this way than.
It's not even a logical assumption in the first place — just one that the _AAs have tried very hard to push. Look at any paid product's conversion rates and then try to say with a straight face that every illegal download is potentially a lost sale. The "potential" is extremely low, similar to how every trip to the supermarket is a potential mugging. I would guess that only one in fifty is even potentially a lost sale in any meaningful sense. (And that's not even factoring in the converse truth that some percentage of piracy actually amounts to gained sales from the pirates either paying for a later version or getting their friends to do so)
Regardless of your stance on piracy, the "illegal download ≅ lost sale" numbers are not remotely reasonable.
In games, pirates seem to outnumber legitimate customers roughly 9:1, but pirates convert to legitimate customers (in the face of DRM or other obstruction of the pirated form) at a rough rate of 1 customer per 1000 defrayed pirates.
Saul Williams had a relatively contemporary offering of a free/$5 album that in two months (and with producer Trent Reznor's extra exposure) sold as many copies as his previous album had sold in four years while garnering four times as many free downloads. He's had two albums since, but I don't know what the sales are like for either of them.
It's also worth noting that there were a fair number of torrented downloads of both albums, which should shift numbers closer to the observed game piracy numbers.
This has been debunken countless times. I think there isn't anyone but the RIAA to still pretend this.