Kids hiding a stash seems to be the most likely explanation for how all those porn mags wound up in the woods. Could also be a guy who didn't want his wife finding his stash, but kids seem more likely. Did they do their porn perusing in the woods, or look at them somewhere else and just use the woods as a stash spot? It's possible that they'd peruse in the head (what we Sailors call the restroom) at school, and then look for a convenient place to hide the stash on the way home. As for their use, if they were found out in the woods, I'd also be concerned with how heavily they are (were?) weathered. As long as there is no heavy wear from weathering, the pages are relatively clean, and none are stuck together, such a find could actually be a decent score.
On a somewhat related note, I did quality-assurance at the Gallo winery a few years back. A truck came up to my platform, and it was obvious that something flat, round, and reflective was in one of the bins. The boss looked at me and said, "CD, DVD, or porno?" I said, "That's a fuckin' porno." He grabbed a pole and fished it out. Sure enough, it was a porno. I don't remember what, exactly, it was...but now that I think about it, how and why did it wind up amongst a bunch of staked grapes?