You regard finding out whether someone you have sent a marketing email to actually opened that message as 'morally reprehensible' somehow? I know that blanket surveillance and government intrusion is a bad thing, to be minimised, but I'm not sure that also makes recipient tracking for one's own marketing purposes evil. If done right, cookies, email bugs and similar technologies are benign, or even beneficial to the recipient... It's all about finding out what the customer actually wants by observing what they do, since when you ask them, they often don't really know.