With the newest tragedy at Virginia Tech of two students being shot and killed at a campground the question of safety in the woods must be asked. While the deaths are a horrible tragedy, the state parks, national parks, and county parks report very low crime rates.
Most crimes happening in parks include vandalism, drinking alcohol where prohibited, and littering. Pennsylvania state parks reported 100 arrests in 2000 in all of the 116 state parks. And with hundreds of thousands of visitors, that is a very small number.
Always, hike, camp, or backpack with a buddy or a group and let someone back home know where you are going and when to expect you back. You should use these practices regardless of the fear of perceived crime or not. Things happen when you're outdoors; even a sprained ankle can immobilize you at times.
Getting outdoors is too important to let an isolated incident discourage you. Keep hiking, camping, fishing, paddling, or whatever you do outside.