Northwest Airlines Promotions
Leave aside that NWA just cancelled my flight out of Denver tomorrow (so much for being unaffected by labor issues -- but they did rebook me on United an hour later). The RSS feed on this page tells me they have some smart people (or, more likely, smart business partners -- expedia used to do their web pages).
I'd never sign up for NWA promotions via email. That would have the same effect on my email as spam. On the other hand, a bookmark in my bloglines web-based RSS reader is another story. I can click on it when I like, clear it when I like, it's in my new 'marketing' folder, it's just useful.
Amazing it's taken this long to happen.