Not really, but if it falls then yes you'll need one.
No nothing but the your skin works on an iPod touch.
No.
No. The new iPod Touch 4G's are slimer than the 3G and a hard or soft case will not fit them.
You must use your finger (or other parts of your body made of skin) for all actions performed on the touch screen of your iPod Touch. It has been designed to only recognize skin and not touches from objects in your pocket or other annoyances. As a consequence, styluses and fingernails do not work on your iPod Touch's screen.
Bestbuy
There are few awesome accessories available for the iPod touch, which includes a USB power adaptor, earphones, and a skin cover (case.) You could also buy a travel cleaning kit.
Found myself an answer actually... http://www.zagg.com/invisibleshield/index.php
covers or stickers that help protect your ipod.
It depends on the type of skin you get.
There are several types of "cases" available for an iPod touch: Skins, shells, and true cases. Skins are basically a thin layer of material that goes on the iPod and changes its appearance. Hard shells are pieces of plastic that snap onto the iPod and help protect it from damage. Finally, cases are usually made of silicone rubber and are like shells in that they protect the iPod, except that they are flexible and can help absorb impacts. A skin will cost you about $20, a shell about $30, and a case about $40.
the skin receptor that helps us to touch is our skin receptors
Touch and pressure sensations are initiated in the skin.