Interesting article.
I think with the Friends line expanding recently, these sorts of letters are getting more common.
I think some of the Friends sets are awfully stereotypical, but others aren't too bad. Remember the Belville line? The sets had ridiculous Price-to-Piece ratios and the designs weren't usually that good. Whereas Friends has some good designs and the prices are about average.
Also I noticed one of the items on the list read 'Stop blowing everything up'. Is this referring to some of the play features TLG always adds in?