There have been isolated incidents, but you're going to get them anywhere. There was a minor problem with people on bikes approaching people and stealing things then taking off, but this appears to have been resolved as I haven't heard about it in quite some time. There have also been isolated incidents involving a person who was approaching people then revealing himself to them, and while I find that somewhat comical I'm sure it'd be rather traumatic if it happened to me. Apart from that, I haven't really heard reports of anything else.
I think mostly though it's a precaution, it's a big campus and when you finish up after dark it can sometimes be intimidating when you have to walk to the other side on your own. The security phones are all over the place, so if you're at all worried you can call for an escort. It's a nice idea and seems to be utilised by lots of people, so if you're at all concerned you shouldn't hesitate to use it. Better safe than sorry, as they say
