There are plenty of great and effective digital marketing channels, but there are just as many bad ones. Or at least good channels that tend to be used poorly by lazy marketers. These are our six least favorite marketing channels.

• Direct mail: because it’s usually useless and hard to track.

• Spam email: Email marketing can be great, but it too often isn’t.

• Bogus LinkedIn connections: Don’t connect with me if I don’t know who you are.