Why would someone use port 80 for deployment of unauthorized services?

Google will detect the service listing on port 80 and post a link, so that people all over the world will surf to the rogue service.

If someone were to randomly browse to the rogue port 80 service they could be compromised.

This is a technique commonly used to perform a denial of service on the local web server.

HTTP traffic is usually allowed outbound to port 80 through the firewall in most environments.