Today I was going to make a thread on Final Fantasy XII, but I chose not to incase anyone added spoilers which would ruin the storyline for me.
I think it would be a great idea to introduce a [spoiler] tag to use in the forums which will make the embedded text invisible automatically and can be read by highlighting it. Here are some examples:
Board Message
This might actually increase the amount of users discussing things as they will know that they do not need to avoid it incase there is something mentioned that will ruin the game/movie/tv show for them.