If you noticed most phones have some sort of indicator on the #5 button. My home phone has this as well, it lets people know which button is 5 in the dark or for people who are blind?
It's also useful if you are trying to type without looking to type fast so you can find the numbers. When you put the Blackberry in your hand and get used to typing letters without looking I find it's still hard to type numbers and I need to become accustomed to the bump.
