ouch... I raced in the cat 4/5 for the Greensburg, IN race this past weekend and there were 3 guys that I thought were new to racing, but I try not to judge so I moved past that thought and onto thinking about the race. About half way through the first lap, I'm pretty certain these three were involved in a crash that took out a significant part of the group. I can't be 100% sure because I was on the side of the them (just by luck) but a fellow teammate later told me that the only reason he wasn't involved was because he saw these three guys getting sketchy in the middle of the group and moved behind me. He said they were getting too close, bumping shoulders etc.. and finally one of them went down taking the others with them and most everyone behind them in the group.
As I move up in categories, this won't be a problem but I've learned to go with my first impression and stay just outside of striking distance of the newbies--at least for a lap or two and most definitely during climbs and sprints. I realize ANYONE can cause/have a crash regardless of experience, but why put myself into a position that has greater risk of a crash?
I'm always amazed at how loud a bicycle crash is, even if it's just one person.