Finger-size keyboard on a small screen

It looks like we want to do use our fingers more and more when we interface with touch screens. Is it because we are so used to have our fingers involved due to keyboarding or is it the tactile sensation?

The pen has been used for centuries to write, the fork has been used for a few centuries to eat (I am not sure how long the chop-sticks have been around): Tools that are quite useful I would say. -:)

It is true, we still use the finger to write on a dirty window or in the sand, we still use our fingers to eat sandwiches and pizza,... but not spaghettis. What do we want to do with a finger on a PDA: switch applications, switch windows, write? Write how much?

What are the reasons not to use the pen on a PDA?
1. We lost the pen.
2. We don't care about screen space to see what we write.
3. We don't want to put on our glasses.
4. We don't need all the keys for what we write.

These may be good reasons to create a finger-size keyboard. What do you think? Can you think of other reasons?

Just brainstorming -:)

Marianne