Merriam-Webster lexicographer Kory Stamper of harm•less drudg•ery has an entertaining but pointed blog entry about dealing with the sort of people who take the dictionary as an authority on things for which it isn’t one.
Ten years ago, we added a second subsense to the noun “marriage” that covered uses of “marriage” that refer to same-sex unions. Someone eventually noticed.
Outrage! screamed about 4,000 emails, all flooding my inbox in the space of a week. How dare you tell us that gay marriage is okay now?
I was not surprised, honestly: I drafted a long, thoughtful reply about how words get into the dictionary, noting that this sense of “marriage” had been used by both proponents and opponents of same-sex marriage since at least 1921, and finishing with the caution that the dictionary merely serves to record our language as it is used. I spent the next two weeks doing nothing but sending this reply out to everyone and their mother.
But that wasn’t the line that made me laugh out loud at my computer. That line was this one:
As for the dictionary being a moral guide, it never was and it never should be. We enter the words “murder” and “headcheese” into the dictionary, but that shouldn’t be read as advocacy for trying either one of them.
Anyhow — go read the whole thing. It’s good.
Dr. Doyle's Blog 
This is good too – Re-imagining the Dictionary with Erin McKean. http://www.ted.com/talks/erin_mckean_redefines_the_dictionary.html