Interesting idea brought up during a conversation regarding the benefits of using a PDA as an address book:

What if the number of friends you had was determined by the memory capabilities of your electronic device? Imagine someone introducing themselves, and you have to turn them away, saying "I'm sorry, I don't have any more room in my cell phone for your number." This might be remedied when you realize, "Oh, wait, I haven't talked to this other person in over six months. Let me erase their number and add yours."

Better make sure that you also have a backup somewhere else to ensure that you never lose friends' contact info. Those PDAs are awfully easy to drop (doh!) or lose.

Just a thought.