Made plenty of people jump on either my team or the opposition whilst wearing Flecktarn. One mate says it's like a blur, some simply just don't see you at all especially if you're still.
Then again how many people walk into a room and don't see someone if they're sitting dead still. Movement is a big give away hence why tiny slow movements can go undetected even at very close range. Add silence and it's ninja-tastic.
Think of a Lion hunting, creep, stop, creep, stop. Before dinner knows what's happening it's dead.