Really touchy feely people. For example, I had a boyfriend. One of his close friends was a girl. They'd always be walking around the hallways together, and he'd have his arm around her. It wasn't just her, but he did that with all his friends who were girls. I even saw him "joke" holding hands with someone.
I know he honestly didn't mean to make me upset, but what the hell? I'm not even the jealous type, but I believe there is a certain line that shouldn't be crossed when someone is "taken".
I have a real problem when the difference between me and my boyfriend, and him and another friend whose a girl, is the title "boyfriend/girlfriend", or kissing.
What makes it special, if you're going to put your arm around, and hold hands with every other girl?
Seriously. Keep your hands to yourself. You can be friends with the opposite sex without putting your hands everywhere.