Funny that. I've only ridden through Epping Forest once in daylight and indeed there was a "porn mat" . Hadn't seen one since I was a nipper.
Highlight of our childhood forays into the woods was the inadvertent discovery of discarded pornography. I had assumed the internet had put an end to that. I am pleased to hear something of yore has survived into the great information age. It's like finding your fax machine still works (and that's what the beeping noise is). Well, actually, when you're thirteen finding porn is probably a lot better than finding you've got a very out-of-date fax waiting. Possibly this rule holds when you are 37 too.
Litter does piss me off though. On a ride the other day, some idiot just threw a half-full coke can out of their car window, leaving it to bounce down the road. Popping into Tesco on the way back, the usual 4x4 driving ijit in the disabled spot happily shoved the wrapping from whatever they were eating out the window before driving off. This is fairly typical. And this, being south London means there's drifts of fried rat packaging everywhere, along with the drink cans and other sundry accompaniments. Left to our own devices, given a couple of weeks, we'd be neck deep in fast food detritus. Archeologists of future will identify us by the compressed layer of discarded Morley's Fried Chicken boxes. We'll be Morley-Man. A horrible, horrible thought and legacy.
And of course, if you've got an old TV, stereo, fridge, whatever - the two best ways to dispose of it are to leave it around the corner, or find the local green area and lob or lever it over the fence for everyone else to admire.
I always pick up what I can (litter, not porn) but it doesn't seem to make much difference.