I've found 3 total. They appear in the Stinging Winds of act 2. There will be a guy by a boat saying something, then a ton of suicide bombers pop out and kill him. It always seems to be on the north side of the map. I'm running it over and over to see it I can make it appear.
I have a feeling once all of these are collected, they will have a use at SOME point in the game. Might not even be until the expansion, who knows.. but I'm not risking it by getting rid of them. Don't you think it's odd these are physical items, instead of tacked into your journal with the rest of your discovered lore?
"There is nothing good or bad, but thinking makes it so." ~ William Shakespeare