With the new Jailbreak for iPhone, the guys at Beamn.at have added a Cydia repository to allow very simple installation of the new Flash (called "Frash") iPhone functionality.
In theory this is one of the last barriers to the iPhone for the non-believers, other than of course "well Apple should have made it standard!". If you want flash ads on your phone that badly, you now just need to Jailbreak your phone and install the app and voila!
No word on battery life, functionality, etc. I'm going to guess that the app is still fairly alpha, and of course the standard disclaimers about Jailbreaking voiding your warranty, potentially making your phone less secure, and making your mother feel bad all apply.