I've heard that some apps may make it a little too easy for some users to accidentally up/down vote without realizing. I've definitely caught a few accidental votes myself, so I'm not sure how many more I didn't notice. Also, totally random anecdote, but the pockets in my "house pants" have a weird fabric that combined with the on body detection to keep my phone unlocked sometimes allows my thighs to "butt dial" if I put my phone in my pocket with the screen facing my body, and I'm sure other people have similar stories about accidental inputs, so I wouldn't worry about it too much.