It's important to note that most of the horror stories involving Tor nodes are related to "exit" nodes. These are the nodes that bridge the open internet with the Tor network. As such, you can see what traffic is traveling through them much more easily.

It's not recommended to run exit nodes if you don't know what you are doing and have a fair bit of resources (time/money) to spend on it. Without exit nodes Tor doesn't work, but they are risky to run because you can be held liable for the content traversing the machine.