Mar 31, 2016 - HubSpot Blog/Excellent Information: "When Do People Unsubscribe From Email Marketing Campaigns? [Infographic]"
from HubSpot's March 25th posting:
"...an unsubscribe isn’t the end of the world. In fact, it can actually serve
as a helpful signal. For example, if you notice that your unsubscribe rate is starting to climb, it might mean that you're
overloading your audience or failing to target them with sufficiently relevant content."