If it is of any interest:
I have no view particularly on this topic but I happen to be one of those people that also gets mailings from the guru's.
As I only accept text mail and block HTML, I have cancelled some lists recently that do not include the text, or that only include a link to a webpage.
I feel it an invasion of privacy to even try and monitor anyone opening their mail.
Incidentally I am also one of the people that blocks popups and animation on web pages. I don't open mail for pretty pictures and if I want animation I would watch a video.
May I suggest that if anyone has anything decent and interesting to say in their mail, that they keep it plain and simple.
Newspapers keep it plain and the trash mags use the fancy graphics.
Just a personal view,
Regards.