.
Contributing to a thread, seeing it grow, many good posts in it, some distracting ones, and then POOF! it's gone.
If only this software had thread splitting, all the off topic gripefests could be split off into some Neverland place, and the rest of the thread left as valid, and available.
It seems when someone (more than one) don't like a thread they start crapping it up to see if they can get the whole thing hidden.
It's a pain, and discourages from contributing.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic