Niantic updated the official website of the Pokemon GO at the FAQ part. With the updated part now you can read the reasons why Niantic can suspend your account in the future.

Based on the website, Niantic can suspend a Pokemon GO account immediately without any notification: illegal position manipulation, emulate or / and using remodeling software, using additional illegal informal software.

Next to it Niantic started to working on an anti-fraud system which going to protects some ways the players and going to improve the quality of the game.