A guy at the last university gym I went to was severely guilty of #1. He was a super nice guy, but he just had a consistently bad habit of using way too much weight. He'd grab the 90 or 100# dumbbells and would, as mentioned above, swing his entire body to get the things. He'd then repeat this process for a good 3 or 4 reps. He also did the equivalent of this on benchpress. I remember having to spot him one time--I had to basically deadlift the bar off of his chest after the first rep. He then wanted to do five more reps. No clue what he thought he was getting out of it.