Along with all the others here, I also immediately unsubscribe and get rid of products that feel like they're a bit too close for comfort. My side project is now making a lot of money, and people value tremendously not getting newsletters, or messages from John, the customer superhero. There is value in email, tremendous value, but I strongly believe that it's timing, wording and situation that will get you the most mileage here. I send one single email after about a week of no user pulse, all it says is: we still have your data, looks like you may haven't had a chance to try this yet, here's a coupon that expires today and it'll get you some extra credits (or whatever your product offers). If not interested, simply remove your account by clicking here.
No point in storing dead accounts. I don't care about a falsely inflated user base. People love that.
Also, I end the email by saying, "click reply to talk to our CEO directly and ask any questions you may have."
The last one gets a lot of conversions, and helps tremendously in figuring out what their concerns are.
This system is doing the magic for me.