Apple love the fact you jailbreak...
If Apple had somehow managed to make the iPhone v1.0-1.4 jailbreak proof, how popular do you think it would be today?
Remember that the jailbroken iPhone enabled:
Countries who weren't on the "global" rollout could get it.
People who weren't prepared to change network during their other network contract were able to use it.
3rd party Installer of other Apps, the AppStores older brother.
The jailbreak community has opened up the Apple to a worldwide audience, many of the developers on the previous Installer applications (MooCow etc) have come under the Apple umbrella, embraced (?!) the App Store and the chance to actually profit from their skills.
I hope Apple aren't so arrogant to realise this, and I think their strategy of continuing to pretend to lock things down with newer version numbers is just a PR strategy to look like they are trying to act on these "jailbreaking hackers", but really, although they could calculate a jailbroken iPhone as a potentail loss of revenue, they also recognise that similar to Microsoft, if they did actually completely lock down their software, they wouldn't get the global footprint that they are looking for. (Don't tell me that MS couldn't lockdown their software if they really wanted to).
So let the game of cat and mouse continue on.
As time goes on, and 3rd party developers carry on pushing the iPhone to the limit, for example, xGPS are about to release proper "turn-by-turn" Sat Nav for the iPhone, wait and watch Apple take advantage of this and before the summar, Apple will have released the new version of Google Maps, which will be a reverse engineer of the unofficial app which will go through the bug fixing staging much earlier, allowing Apple to release a decent quality version of it.