Answer:
It's harmful because people could be advertising things that could scare or hurt people. Also some people advertise fake things to get your money and to trick you.
Step-by-step explanation:
1. Advertise things like drugs and alcohol. It's bad for people and it could harm them.
2. People can scam you into buying things from them and get your information because you tried to buy it. They can get your cards, money, address, and other things.