A fake account can be defined as an account that is either not a human being (i.e. a bot trying to get trust in order to issue tokens) or as a person who is trying to create many different accounts in order to issue tokens. Those accounts won’t have the same trust network as real human beings, and the system detects it and handles their tokens differently, giving them much more limited usability. If you accept such tokens by trusting these (fake) accounts, you probably won’t be able to spend them anymore.
This very complex tracking and calculation are only possible on the blockchain - that’s why we use this technology.