3ROD only occurs on random, and like any other electronic equipments it just the matter of luck..but it also can occur if:

1. the owner is lacking the habit to clean his/her room, thus transforming the console into an expensive dust collector thingy..
2. ventilation..cramp ur console in a tight corner, play it over night, and tomorrow morning u'll have a brand new paperweight..

juz becoz we have a dedicated thread to discuss this kind of thing in the Xbox forum it doesn't mean that 3ROD occurs too frequently, and also if by any chance 3ROD happens to ur console u can always send it back where it came from(or to experts) for repairs..

peace!