It turns out "15% of all passcode sets were represented by only 10 different passcodes"
Some people just don't care if their phone is secure, and thats fine. I'm posting this to help the people that do care and think their commonly guessed passcode is enough. As my friend's dad said to me when I was 15 and proclaiming that I had the best bike lock sold (I didn't), "Locks only stop honest people". It still doesn't hurt to know where you stand with security though.
Source -> http://amitay.us/blog/files/most_common_iphone_passcodes.php
On a related note, secure your wifi at your house with a modern encryption method (instructions below), NOT WEP. It honestly is very easy for any body who can use a computer, just follow the directions. Even though most security methods are crackable by somebody determined enough to get in (and probably sitting in your driveway with a laptop on their lap), its very easy to put in a tiny bit of effort to push away 99% of all threats.
How to -> http://arstechnica.com/guides/tweaks/wireless-security.ars via http://lifehacker.com/386675/secure-your-home-wi+fi-network