We all know Apple likes to keep things simple. Their modus operandi has always been "we are anti-button". That has lead to some great leaps in industrial design and powerful products that are ridiculously easy to use. It is my opinion that, in one instance, they went a bit too far.
If you are browsing a contact list and your finger slips, it dials a number. Touch a call from your recent call log and it dials instantly. When using a Web application or one of the new native iPhone applications, touching a telephone number places the call immediately. Apple made it very easy to place a call, even if it is unintentional.
My proposal is to add a setting (hidden in the Settings widget) that allows you to set whether all apps or just certain apps can dial a telephone number without user interaction. Otherwise, a modal window pops up and says "Call (555) 555-1234?" In fact, it would be helpful if you could do this from the included Contacts application as well. If you are using the touch pad, there would not be a need for the confirmation.
If Apple does not want to add it to the firmware, at least application developers could include such a prompt in their product. Until then, if you get a call from me and I immediately hang up, please forgive me.