Could iOS 5 include deep, system-wide Twitter integration? It could if TechCrunch and Daring Fireball are correct. First up, MG Siegler rumored:

We’ve heard from multiple sources that Twitter is likely to have a big-time partner for such a service: Apple. Specifically, we’re hearing that Apple’s new iOS 5 will come with an option to share images to Twitter baked into the OS. This would be similar to the way you can currently share videos on YouTube with one click in iOS. Obviously, a user would have to enable this feature by logging in with their Twitter credentials in iOS. There would then be a “Send to Twitter” option for pictures stored on your device.

To which John Gruber added:

Imagine what else the system could provide if your Twitter account was a system-level service.

We've seen Apple work with Twitter on Ping integration after their initial efforts with Facebook fizzled. If iOS 5 includes Twitter as an option in the Action button, the way it does everything from email to MobileMe to YouTube today, is that interesting? Or is there something beyond even that?

[TechCrunch, Daring Fireball]