I was surprised to see that Apple’s iMovie iOS app runs on my iPhone 3GS (not jailbroken), even though Apple does not officially support it. It makes me wonder if it is just a stunt to get people to buy new iPhones.
How It Got Installed
Somehow the “automatically download Apps purchased on other iOS devices” option got selected, so when I installed iMovie on a iPhone 4S, it downloaded to my other iPhone 3GS without the normal compatibility checks.

How It Works
It seems to work fine. I was able to edit a video sequence and export it properly. I guess it probably took longer to export than on a new iPhone, but the point is this: it worked. It does not really need a front facing camera.


Errors Updating Software
When I open the App Store to update software, I can no longer use the “Update All” feature, because the phone immediately objects saying, “This App Is Incompatible With This iPhone: This app requires a front facing camera.” Instead I have to s-l-o-w-l-y select each app individually and click the Update button in each detail screen.

Corroborating Evidence
I cannot prove that I am not making this up, but here is at least a screenshot showing the model number MC137LL iPhone that I have. (Image lost – see Digital Dark Ages)


Conclusion
Since the iMovie app seems to work fine on the iPhone 3GS, I have to wonder if the most probable explanation is that Apple is pulling this stunt to get people to buy newer iPhones.