I used to write that my pages had spoilers but after a while, I realized that no one else did and they totally cut up the movie, so I just stopped. I always just assumed if you go on this site, you should be aware a page is likely going to spoil things for you. I sympathize with you though, it sucks when a movie you want to see gets spoiled. (I don't look anywhere other than actor ID on IMDB since some dick decided to spoil Gran Torino for everyone).
Usually I end up spoiling it for myself though.
If you look at The Mist page, I did warn people that the page spoiled the ending, because all of the guns take place during the ending. Plus, the movie is totally ruined if you know the ending.
And P.S. I really like how the "SPOILERS" bars cover up such info on IMDB. While it could be harder to make pages, such an ability would be cool. I wonder if this site is capable of it.