Searching on Newegg for "raspberry pi", the results included many heatsinks and as well as a few other types of cooling systems, yet these items do not seem to appear when looking through the stores of the official distributors.
Does the Raspberry Pi need some sort of cooling system for its processor such as a heatsink? If one is not always required, are there special situations where a cooling system would be necessary (operating in an outdoor environment where temperatures may reach 35°C during the day)? Or is the temperature more related to how hard the processor is working?
Do home-made cases for the Raspberry Pi need to include some sort of ventilation or fan to avoid temperature buildups?