I'm pretty sure pg doesn't post the criteria being marked "dead", but I thought I'd heard one time that it took ~10 flags for it to happen.
After my original post to the petition was killed, I thought I had done something wrong linking directly to the petition...as if that was some sort of spam (e.g. linking to an article about a product vs. linking to the actual product page seems to be the norm here as most direct-to-product links come off as spammy).
I'm assuming good faith about the whole thing, but think that it's an interesting gray area ripe for community discussion.