Maybe this is, like, email marketing 101 (and if so, please leave a comment), but the introductory series of four emails American Airlines sends to its new frequent flier members struck me as unusual. Wonder what it does to open rates.
P.S. It wasn't technically spam -- I consciously subscribed for AA's mailings -- but these guys are very prolific writers.
Original Post: http://adverlab.blogspot.com/2010/03/spam-serialized.html