Sometimes it's annoying...
I don't want to come off like a major geek but sometimes it gets difficult.
For example, recently an associate was doing a crossword puzzle. One of the clues was, "The director of The 39 Steps.. I nearly answered but this guy said, "Clint Eastwood!"
Whaaaa? I wanted to interject and tell him how wrong he was but I kept quiet. Her crossword was ruined, though. =(
Is it better to keep quiet or should one break out the movie knowledge whenever?
Mood: 
Bored
Bored
I agree with Rusty, most people are grateful for help and some are impressed by movie knowledge.
Neutral
Break out the movie knowledge.
Never let a perfectly good crossword puzzle get ruined.
When someone shouts out an answer like that, tell the "crossworder" the correct answer quietly and leave the room, laugh uncontrollably and when you're done wiping your tears away, return and see how the crossword puzzle is going.
We accumulate knowledge for many reasons.
One of them is to help solve crossword puzzles.