My whole time I've been here I feel like half my posts are correcting someone about a movie when it's not actually found footage. I feel like a dick when I do that but I just can't help myself lol. The most common ones I see and correct others on are :
End of Watch (only a few scenes are shot with Gyllenhaal's character's camera)
Chernobyl Diaries (the opening shots are filmed with a camera, which seems to set it up as a FF but only one other scene is, when Jesse McCartney's character is in the van and his girlfriend is recording)
District 9 (about 30-50% of the movie is news reels/mockumentary type, but a lot of the movie is not a traditional FF)
Skinamarink (unless the little kids are operating the cameras, it is not FF. Just shot in a weird way haha)
Can't think of any more off the top of my head, but these are the most common mistakes!