In the SMBus spec it says:
The I²C specifications do not require that a device always acknowledge its own address. This can confuse a system controller. If a device does not acknowledge its own address how does the system controller know if it is because the device is busy, has failed, or has been removed?
This sounds a lot like blackening I2C, and I'm not used to see this kind of language in a spec.
Besides, I think SMBus is lying here. In I2C the address byte must be acknowledged just like any other byte. Or must it?