There are probably more, but I stopped counting at two: Fringe, and the Hunger Games.
A few months ago, I was flipping through some links, probably on io9 or Chud, and read some article about the unanswered questions in the previous season of Fringe. I hadn't watched any episodes before, despite my interest, and figured that I would probably not get around to it until the series ended or was cancelled in some untimely fashion. The Old Lady and I have continued her policy of almost never checking the NetFlix queue, and one day disc one of season one of Fringe showed up. I wasn't really annoyed by the knowledge of the few tidbits that article had given me, but then I had to look up whether Fringe was still on the air since we don't get Fox on a regular basis with our previously-urban-now-decidedly-rural broadcast antenna. I couldn't find the information I wanted fast enough through other means, so I clicked through to Wikipedia. Suddenly, I found myself in an Arrested Westeros moment: I've made a huge mistake.
The truly moronic aspect of this story is that I ruined The Hunger Games in EXACTLY the same way about two months prior, and had resolved not to research anything I wanted to consume on Wikipedia. Books, movies, foods, etc, everything can be ruined forever.
The Hungus Games are probably in production now, or may even be available on Pay Per View at your local hotel.