Conversely, it is the basis for pragmatic advice for companies or non-profits that manage to get someone to subscribe to a newsletter: Don't send a newsletter for the sake of sending one!

Non-profits that send monthly updates that merely highlight a member are particularly infuriating to me. Tell me of a new project when it launches or a big milestone reached. Letters sent for the sake of "just checking in" make me ignore subsequent emails. I get newsletter blindness almost as fast as ad blindness.