By this point, I feel bad for the person at Wiley who wrote the letter protesting the use of ____ FOR DUMMIES in a blog post title. BuzzMachine is now organizing a protest encouraging bloggers to end their posts with a FOR DUMMIES. Details here.
Background here.
Without speaking to this specific case – many owners of trademarks send out letters motivated by a speculative theory that unattributed non-commercial use of their trademarks dilute the value of their trademarks. In the era of the blogosphere where lawyers letters get posted and linked to, some trademark owners may be trading the possibility of dilution for the reality of tarnishment.