Fever is a response to infection. The fever itself is rarely dangerous, as your body has a "shut off" to prevent your temperature from rising to dangerous levels.
That being said, fever in children, especially infants, can cause seizures if it goes too high.
My mom was an RN and she always told me that a fever of 100 degrees will "burn" out the infection just as well as a fever of 102, so she always gave us fever reducers when it got to 101 just to make us more comfortable. Does this mean if you give a person fever reducers at the first sign of an elevated temp you are just prolonging the illness because there's no fever to kill the infection? I don't know.
But with my kids, I try to take the middle road and let the fever do its job but keep my kids as comfortable as possible.