Haven't actually done this, but my current favorite idea is to ROT-13 the text, paste it into TextEdit, take a screenshot, save the file, zip the file, and then post it on a slow server.
Probably best for everyone that I never get a chance to implement that...
Government-mandated RFID chips implanted into people's brains. People will just do it without knowing why. Best part is, the chip can be updated by satellite.
Why not just wait until after the show is over or you've seen the movie to click on the link? I don't even look for a spoiler tag, I just automatically assume there will be. That's what I do for the Lost thread, or any threads for movies I've haven't seen yet.