updated 03:26 pm EDT, Wed March 19, 2014
Apple forces users to pick carriers with official deals
iOS 7.1 appears engineered to block people from using the iPhone's Personal Hotspot (tethering) feature on carriers without official support, complaints on Apple's support forums indicate. Previously it was possible to manually edit APN settings to connect to any carrier. Since that editing is gone, though, tethering has been limited to the smaller number of carriers that officially offer Personal Hotspot.
While some people have used APN editing to avoid paying extra fees for tethering, the issue is a more serious concern for people using an iPhone on a carrier that does allow tethering but is without an official iPhone deal, which can include some BYOD (bring-your-own-device) providers.