So, I sign up to release applications through the App Store and "Bonjo Nelson" offers different apps through Cydia on jailbroken phones. As long as I'm not daft enough to try and punt the same app through both channels, who would ever know?
Anyway, I use the jailbroken phone not because of any abstract love of freedom, but simply because it does things I need that the vanilla iphone doesn't
1. I have unlocked it using the wonderfully named yellowsn0w application so when I'm in the US I can use my phone with a cheap AT&T pay as you go card (as my phone is O2 Pay & Go, it doesn't work in the US even if I wanted them to rape my credits each time I made/received a call). Funny how I thought I paid for the phone without it being on a subsidised contract, yet it's still locked.
2. I can run an http server on it, lighttpd, and have web apps I've created stored on it to use whenever and wherever I want.
3. I can selectively run other apps in the background. Handy for keeping connected in IRC channels, for example, while I go off to check my mail.
The phone DOES crash more than the plain phone with certain apps (well, more specifically, the apps run out of memory and bomb out), so I can understand why Apple are reluctant to let the great unwashed do this, but I'm prepared to put up with this in return for the advantages.