Apple is not releasing the iPhone 5 for sale by mobile operators until they've confirmed the system's performance. Originally rumored back in October, and now confirmed by Swisscom; it puts Apple into a unique and unprecedented position of essentially holding an operator hostage until their network is up to Apple standards.
In a way this is understandable. The days when you bought a phone from a carrier and then got support from that carrier are long gone. If you're operating an iPhone 5 on Verizon and encounter problems, you're more likely to call Apple than Verizon for support. So Apple, wanting to reduce support calls, needs to insist that the network perform adequately before approving products. The operators may not like this (maybe even for ego reasons) but it makes sense.