Well, engaging in raw sex with anyone you just met is risky, and playing games with your body, health, and well-being. You open yourself up to a lot of STDs/STIs and even HIV/AIDS. Even though the chances of HIV are low between heterosexuals, it doesn't mean it can't happen.
It's understandable to be concerned about your friend's well-being; you wouldn't be a real friend if you weren't concerned about him and the way he's moving; people should always strive to use protection during the first few sexual encounters to be on the safe side.