People and businesses send crappy emails all the time. We tolerate it because there is some value being exchanged or because we have some type of relationship with them, but ultimately if you don’t respect your audiences’ time and attention they’ll unsubscribe the second they think they can get that value elsewhere or if they just get annoyed enough.

Seth Godin wrote something related to that back in 2011 (links here and here) calling it the “attention economy.” With technology increasing the things that demand our time, it’s an idea that will probably continue to grow in importance. 

The most important thing to keep in mind with email marketing / newsletters is that while they are usually labeled as owned properties, they are also earned via the trust of your audience.