Specifically the matte black model.
An online discussion on the Apple forums pointed out an increasing number of iPhone 7 owners (specifically the matte black variant) are complaining about the black paint chipping on their devices. A similar issue happened when the black variant of the iPhone was released a few years back.
One user said that he barely had his iPhone for less than a month and used it with a protective case when he noticed that the black paint has started to come off revealing the silver colored aluminum shell. It was initially thought to be dust, but it appears that it’s the black paint that’s coming off.
It was mentioned that normal chipping could occur on smartphones like the iPhone 7 – but that usually happens years after you make the purchase, not right after you buy it.
I personally own the matte black iPhone 7 Plus since September and have not noticed any chipping (yet).
Apple hasn’t released a statement on the issue so if you own the matte black variant of the iPhone 7, it’s best you keep it in a case to prevent chipping.