Pokemon Go cheating, also known as spoofing, is a fiercely contested subject within the Pokemon community. Despite its prevalence, some query whether Niantic even issue bans at all.
The most common form of Pokemon Go cheating is spoofing. This involves manipulating your phone's GPS signal so that you can go anywhere in the world.
This means you can go anywhere on a whim, which results in access to any gym, raid battle and if using an IV-checker access to the best Pokemon with little to no effort at all.
There are other forms of cheating such as auto-IV checkers and multi-accounting, but spoofing is the easiest to do and is the most common.
Niantic detail their policy on cheating in section three of their terms of service. Specifically Niantic list cheating as, but not limited to, the following:
According to Niantic, yes.
Although it is difficult to find, there is a three-strike policy buried in the Niantic help section. The full details of this policy can be found in the image below, but the short version is strike 1 results in a warning, strike 2 is a temporary ban and strike 3 would be a permanent ban.
While this is the official policy, many rightly question whether it's implemented properly.
It seems all Pokemon Go trainers know someone, or a group of trainers, that frequently cheat in some form. The vast majority receive no action against them.
Conspiracy theorists believe that Niantic purposely ignore the cheaters for two reasons. Firstly, spoofers are among the most hardcore Pokemon Go trainers and therefore spend more real money on the game. Secondly, the Pokemon company want as many players playing as possible at all times.
Anecdotal evidence suggests players do get banned, albeit on a more temporary basis.
With that said, cheating is likely to be a part of Pokemon Go for the life of the game. If you are a spoofer, you're probably going to be ok. If not, and cheating annoys you, try to ignore and play the game with your own targets in mind, separating yourself from the cheating side.