Not every illegal download is a "lost sale", sometimes they are customers you haven't gotten to yet, or you've failed to service already who tried to buy from you.
A friend of mine downloaded a pirated .pdf of Iron Heroes a week and a half ago on p2p. He was quite enthused about the book and kept up with all the previews, and downloaded it as something to hold him over until he could get a legitimate hardcopy. The moment it came in at our FLGS he happily bought a copy and is already planning two campaigns for it. At another game, I met somebody who actually legitimately downloaded a watermarked copy of IH and printed it out, and he couldn't bring himself to buy a printed hardcopy since it was so expensive, he'd already lost money on buying the .pdf and printing it compared to just getting a book.
As a fan of the d20 Star Wars RPG, I often see or talk to players who want to get into the game, but are hindered by how it's out-of-print and poorly supported. It makes me quite glad I managed to get everything produced for the game while it was in production. The SWRPG books are on p2p, and I know people who have downloaded them, but only after trying their FLGS (sold out), trying to special order them through their FLGS (sold out at the distributor level), trying to buy it on eBay (some sourcebooks sometimes going for over $100), and looking around at used bookstores/flea markets/wherever, and once they've exhausted every legal option they turn to piracy. Frankly, I can't blame them, they haven't deprived WotC or LFL of a dime since they have tried multiple times to get the material through legitimate channels, and been stymied. If WotC would put the SWRPG back in print, piracy of it would probably drop.
Also, a lot of downloads on p2p are downloads of convenienence, not "lost sales". It's one thing to be willing to spend $40 or $50 on a new gaming book, it's another thing to idly scan a p2p network, download a book and look at it. We don't know what happened after those 136 downloads. How many thought it wasn't what they were looking for and deleted it immediately? How many took a quick look and filed it away, probably never to view it again? How many actually poured over it and intend to buy it when it comes out in hardcopy, and feel more confident that it will be a good purchase, and might have even been on the fence beforehand? How many people don't have a FLGS to browse in, so they download an illicit .pdf to preview before ordering it from Amazon or other hardcopy souce? How few of those actual downloaders actually said "I was going to buy it, but now I don't have to!" and are planning on running Army of Darkness games using their illicit file?
Many of the games I've seen on p2p are long out of print, things for long discontinued systems, sometimes for defunct companies, but the sort of things that some gamers could appreciate.