Randy Cassingham's "This is True" got blocked at Yahoo. Users who had to confirm their subscriptions decided they'd rather hit the "This is Spam" button than unsubscribe. A small handful of them got the newsletter blocked for the other 15,000 subscribers Randy had at the service.
I firmly believe that these services should track confirmations, and nuke the accounts of people who report solicited mail as spam.
This is ridiculous. Randy is one of the very few publishers I know who hates spam as much as I do. (He's also one of the people I watch for cool writing techniques. Dude's a genius with the clever turn of phrase.)
I have recommended True here often in the past. It's a great read, and a great example of marketing a premium (read: paid) upgrade version of a free publication.
Randy was the very first person to sell paid subscriptions to an email newsletter.
If your audience likes entertainment, of the witty and thought-provoking variety, help him and them out, and tell them about True. http://www.thisistrue.com
And tell them not to bother if they use a Yahoo address.