Word on the street is that Apple might be, and likely is, intentionally blocking push notifications on iPhones which have been jailbroken. The developers of the application Push-based reminder app NotifyMe have been getting an enormous amount of complaints from their 5% customer base which has hacked the iPhone in someway.
As it turns out, NotifyMe figured out that the reason the app wasn’t working correctly for these users was because they were being denied access to Apple’s Push Notification Server (APNS). Major cockblock. Understandable, but still, cockblock. Especially when it’s screwing with legit applications such as NotifyMe.