Originally Posted by HillRider

Talc won't do anything to prevent pinch flats since they are due to mechanical damage, not slippage. What talc does is eases initial installation as it makes the tube slip into the tire more freely and make it less likely to get hung up between the tire bead and the rim.

It will also keep the tube from sticking to the inside of the tire after it's been installed for a while. Some tubes, particularly thin, light ones, bond to the tire so badly they tear when you remove them.