It has already been controversial. Norton IS no longer offers a "teachable" antispam program. Some users have bemoaned the loss.
Today, by coincidence, I came across a message board that censors users' posts, pretty much the way Symantec does here: by removing offensive words and phrases and then replacing them with asterisks. The difference between how it is done here and how it was done on that site is that the censoring mechanism here is fairly conservative while this site I was visiting uses an engine very similar to that employed by trainable antispam engines. The two sentences I quote show exactly why -- if you do have any kind of antispam filter -- your really, really, really want to check your spam folder occasionally.
Without further ado, here are two sentences taken straight from that site. The less English-challenged should be able to figure out what was taken out and why. The rest of you may have to just ask an English-speaking friend:
"I qui*****ching this show ..."
"Communism a***** finest!"