As a college student, I absolutely love freezecrowd. It's an awesome and safe alternative to Facebook, so I actually feel comfortable putting my last name on it. I especially like how easy it is to choose who can see your profile, message you, etc. I had to jump through hoops to get those settings on other social media sites.
Facebook is quickly losing popularity, and I think freezecrowd will take its place. It's really useful for networking, and for finding people with similar interests! It's definitely a legitimate, safe, and fun site!