I get "about 842,000" results from Google when [searching for that as a phrase][1], so you're right that it is fairly common.  

Some background first.  Dictionaries have both [descriptive and prescriptive functions][2], and depending on the philosophy of the editors, different dictionaries may tend to promote one or the other.  Most dictionaries today aim to be descriptive, but by their very existence cannot help but be prescriptive as well. 

The **descriptive** function of a dictionary is to describe the language as it exists:  what language users say or write, and what those language users mean when they say/write it.  

The **prescriptive** function of a dictionary is norm-setting: once the words of a language are described in the dictionary, it starts to become the standard, possibly stifling innovations in the way words are used.  So for example, parents tell their children to go look a word up in the dictionary rather than just telling the child the meaning of the word as the parent understands it.  People playing scrabble look up strings of letters in the dictionary to see if they are, in fact, considered words.  Writers consult the dictionary to see if, according to the dictionary, they can use a word in a particular way.  

So "tyranny of the dictionary" is used as a cute way to describe the prescriptive function of a dictionary, usually by someone who has been caught using a word in a nonstandard (or "wrong" depending on the situation and how you look at it) way.

It is also a play on words with "[tyranny of the majority][3]" which is widely used, and has been widely used for a long time, in discussions of democracy.  So that definitely gives it a boost in usage.


  [1]: https://www.google.com/search?q=%22tyranny%20of%20the%20dictionary%22
  [2]: http://en.wikipedia.org/wiki/Dictionary#Prescriptive_vs._descriptive
  [3]: http://en.wikipedia.org/wiki/Tyranny_of_the_majority