Joshua Henkin writes a great guest post for Writer's Digest:
OK, let’s dispense with the obvious—namely, that there is a kernel of truth to the old saw “Show, don’t tell.” [...]
But it doesn’t follow from this that a writer should never say a character is handsome or happy. It doesn’t follow that all a writer should do is show. To my mind, the phrase “Show, don’t tell” is a wink and a nod, an implicit compact between a lazy teacher and a lazy student when the writer needs to dig deeper to figure out what isn’t working in his story.
I really like that last bit: looking at 'Show, Don't Tell' as an understood shorthand to address problems in a story. A bit of writing jargon, if you will. Being jargon, it's only useful as a communications shortcut to people already in the business. This means that if we hand that bit of jargon to a brand new writer they will simply take that advice literally, not as the understood 'your story needs work' agreement that it would otherwise be.
And there’s real fall-out. I see it constantly among my students, who are nothing if not adjective-happy. Do we need to know that a couch is a “big brown torn vinyl couch”? We are writing fiction, not constructing a Mad Lib. Yet writers have been told to describe, and so they do, ad nauseum. It’s like the sentence that was popular in typing classes—“The quick brown fox jumped over the lazy dogs.” Well, this is a good typing sentence (it contains every letter of the alphabet), but it’s a bad fiction sentence.
Read the rest of his really insightful piece here: http://www.writersdigest.com/editor-blogs/there-are-no-rules/why-show-dont-tell-is-the-great-lie-of-writing-workshops